1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> 4<title>zstd 1.5.7 Manual</title> 5</head> 6<body> 7<h1>zstd 1.5.7 Manual</h1> 8Note: the content of this file has been automatically generated by parsing "zstd.h" 9<hr> 10<a name="Contents"></a><h2>Contents</h2> 11<ol> 12<li><a href="#Chapter1">Introduction</a></li> 13<li><a href="#Chapter2">Version</a></li> 14<li><a href="#Chapter3">Simple Core API</a></li> 15<li><a href="#Chapter4">Explicit context</a></li> 16<li><a href="#Chapter5">Advanced compression API (Requires v1.4.0+)</a></li> 17<li><a href="#Chapter6">Advanced decompression API (Requires v1.4.0+)</a></li> 18<li><a href="#Chapter7">Streaming</a></li> 19<li><a href="#Chapter8">Streaming compression - HowTo</a></li> 20<li><a href="#Chapter9">Streaming decompression - HowTo</a></li> 21<li><a href="#Chapter10">Simple dictionary API</a></li> 22<li><a href="#Chapter11">Bulk processing dictionary API</a></li> 23<li><a href="#Chapter12">Dictionary helper functions</a></li> 24<li><a href="#Chapter13">Advanced dictionary and prefix API (Requires v1.4.0+)</a></li> 25<li><a href="#Chapter14">experimental API (static linking only)</a></li> 26<li><a href="#Chapter15">Frame header and size functions</a></li> 27<li><a href="#Chapter16">Memory management</a></li> 28<li><a href="#Chapter17">Advanced compression functions</a></li> 29<li><a href="#Chapter18">Advanced decompression functions</a></li> 30<li><a href="#Chapter19">Advanced streaming functions</a></li> 31<li><a href="#Chapter20">Buffer-less and synchronous inner streaming functions (DEPRECATED)</a></li> 32<li><a href="#Chapter21">Buffer-less streaming compression (synchronous mode)</a></li> 33<li><a href="#Chapter22">Buffer-less streaming decompression (synchronous mode)</a></li> 34<li><a href="#Chapter23">Block level API (DEPRECATED)</a></li> 35</ol> 36<hr> 37<a name="Chapter1"></a><h2>Introduction</h2><pre> 38 zstd, short for Zstandard, is a fast lossless compression algorithm, targeting 39 real-time compression scenarios at zlib-level and better compression ratios. 40 The zstd compression library provides in-memory compression and decompression 41 functions. 42 43 The library supports regular compression levels from 1 up to ZSTD_maxCLevel(), 44 which is currently 22. Levels >= 20, labeled `--ultra`, should be used with 45 caution, as they require more memory. The library also offers negative 46 compression levels, which extend the range of speed vs. ratio preferences. 47 The lower the level, the faster the speed (at the cost of compression). 48 49 Compression can be done in: 50 - a single step (described as Simple API) 51 - a single step, reusing a context (described as Explicit context) 52 - unbounded multiple steps (described as Streaming compression) 53 54 The compression ratio achievable on small data can be highly improved using 55 a dictionary. Dictionary compression can be performed in: 56 - a single step (described as Simple dictionary API) 57 - a single step, reusing a dictionary (described as Bulk-processing 58 dictionary API) 59 60 Advanced experimental functions can be accessed using 61 `#define ZSTD_STATIC_LINKING_ONLY` before including zstd.h. 62 63 Advanced experimental APIs should never be used with a dynamically-linked 64 library. They are not "stable"; their definitions or signatures may change in 65 the future. Only static linking is allowed. 66<BR></pre> 67 68<a name="Chapter2"></a><h2>Version</h2><pre></pre> 69 70<pre><b>unsigned ZSTD_versionNumber(void); 71</b><p> Return runtime library version, the value is (MAJOR*100*100 + MINOR*100 + RELEASE). 72</p></pre><BR> 73 74<pre><b>const char* ZSTD_versionString(void); 75</b><p> Return runtime library version, like "1.4.5". Requires v1.3.0+. 76</p></pre><BR> 77 78<a name="Chapter3"></a><h2>Simple Core API</h2><pre></pre> 79 80<pre><b>size_t ZSTD_compress( void* dst, size_t dstCapacity, 81 const void* src, size_t srcSize, 82 int compressionLevel); 83</b><p> Compresses `src` content as a single zstd compressed frame into already allocated `dst`. 84 NOTE: Providing `dstCapacity >= ZSTD_compressBound(srcSize)` guarantees that zstd will have 85 enough space to successfully compress the data. 86 @return : compressed size written into `dst` (<= `dstCapacity), 87 or an error code if it fails (which can be tested using ZSTD_isError()). 88</p></pre><BR> 89 90<pre><b>size_t ZSTD_decompress( void* dst, size_t dstCapacity, 91 const void* src, size_t compressedSize); 92</b><p> `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames. 93 Multiple compressed frames can be decompressed at once with this method. 94 The result will be the concatenation of all decompressed frames, back to back. 95 `dstCapacity` is an upper bound of originalSize to regenerate. 96 First frame's decompressed size can be extracted using ZSTD_getFrameContentSize(). 97 If maximum upper bound isn't known, prefer using streaming mode to decompress data. 98 @return : the number of bytes decompressed into `dst` (<= `dstCapacity`), 99 or an errorCode if it fails (which can be tested using ZSTD_isError()). 100</p></pre><BR> 101 102<h3>Decompression helper functions</h3><pre></pre><b><pre></pre></b><BR> 103<pre><b>#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1) 104#define ZSTD_CONTENTSIZE_ERROR (0ULL - 2) 105unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize); 106</b><p> `src` should point to the start of a ZSTD encoded frame. 107 `srcSize` must be at least as large as the frame header. 108 hint : any size >= `ZSTD_frameHeaderSize_max` is large enough. 109 @return : - decompressed size of `src` frame content, if known 110 - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined 111 - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small) 112 note 1 : a 0 return value means the frame is valid but "empty". 113 note 2 : decompressed size is an optional field, it may not be present (typically in streaming mode). 114 When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size. 115 In which case, it's necessary to use streaming mode to decompress data. 116 Optionally, application can rely on some implicit limit, 117 as ZSTD_decompress() only needs an upper bound of decompressed size. 118 (For example, data could be necessarily cut into blocks <= 16 KB). 119 note 3 : decompressed size is always present when compression is completed using single-pass functions, 120 such as ZSTD_compress(), ZSTD_compressCCtx() ZSTD_compress_usingDict() or ZSTD_compress_usingCDict(). 121 note 4 : decompressed size can be very large (64-bits value), 122 potentially larger than what local system can handle as a single memory segment. 123 In which case, it's necessary to use streaming mode to decompress data. 124 note 5 : If source is untrusted, decompressed size could be wrong or intentionally modified. 125 Always ensure return value fits within application's authorized limits. 126 Each application can set its own limits. 127 note 6 : This function replaces ZSTD_getDecompressedSize() 128</p></pre><BR> 129 130<pre><b>ZSTD_DEPRECATED("Replaced by ZSTD_getFrameContentSize") 131ZSTDLIB_API 132unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize); 133</b><p> NOTE: This function is now obsolete, in favor of ZSTD_getFrameContentSize(). 134 Both functions work the same way, but ZSTD_getDecompressedSize() blends 135 "empty", "unknown" and "error" results to the same return value (0), 136 while ZSTD_getFrameContentSize() gives them separate return values. 137 @return : decompressed size of `src` frame content _if known and not empty_, 0 otherwise. 138</p></pre><BR> 139 140<pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize); 141</b><p> `src` should point to the start of a ZSTD frame or skippable frame. 142 `srcSize` must be >= first frame size 143 @return : the compressed size of the first frame starting at `src`, 144 suitable to pass as `srcSize` to `ZSTD_decompress` or similar, 145 or an error code if input is invalid 146</p></pre><BR> 147 148<h3>Compression helper functions</h3><pre></pre><b><pre></pre></b><BR> 149<pre><b>#define ZSTD_MAX_INPUT_SIZE ((sizeof(size_t)==8) ? 0xFF00FF00FF00FF00ULL : 0xFF00FF00U) 150#define ZSTD_COMPRESSBOUND(srcSize) (((size_t)(srcSize) >= ZSTD_MAX_INPUT_SIZE) ? 0 : (srcSize) + ((srcSize)>>8) + (((srcSize) < (128<<10)) ? (((128<<10) - (srcSize)) >> 11) </b>/* margin, from 64 to 0 */ : 0)) /* this formula ensures that bound(A) + bound(B) <= bound(A+B) as long as A and B >= 128 KB */<b> 151size_t ZSTD_compressBound(size_t srcSize); </b>/*!< maximum compressed size in worst case single-pass scenario */<b> 152</b><p> maximum compressed size in worst case single-pass scenario. 153 When invoking `ZSTD_compress()`, or any other one-pass compression function, 154 it's recommended to provide @dstCapacity >= ZSTD_compressBound(srcSize) 155 as it eliminates one potential failure scenario, 156 aka not enough room in dst buffer to write the compressed frame. 157 Note : ZSTD_compressBound() itself can fail, if @srcSize >= ZSTD_MAX_INPUT_SIZE . 158 In which case, ZSTD_compressBound() will return an error code 159 which can be tested using ZSTD_isError(). 160 161 ZSTD_COMPRESSBOUND() : 162 same as ZSTD_compressBound(), but as a macro. 163 It can be used to produce constants, which can be useful for static allocation, 164 for example to size a static array on stack. 165 Will produce constant value 0 if srcSize is too large. 166 167</p></pre><BR> 168 169<h3>Error helper functions</h3><pre></pre><b><pre>#include "zstd_errors.h" </b>/* list of errors */<b> 170</b>/* ZSTD_isError() :<b> 171 * Most ZSTD_* functions returning a size_t value can be tested for error, 172 * using ZSTD_isError(). 173 * @return 1 if error, 0 otherwise 174 */ 175unsigned ZSTD_isError(size_t result); </b>/*!< tells if a `size_t` function result is an error code */<b> 176ZSTD_ErrorCode ZSTD_getErrorCode(size_t functionResult); </b>/* convert a result into an error code, which can be compared to error enum list */<b> 177const char* ZSTD_getErrorName(size_t result); </b>/*!< provides readable string from a function result */<b> 178int ZSTD_minCLevel(void); </b>/*!< minimum negative compression level allowed, requires v1.4.0+ */<b> 179int ZSTD_maxCLevel(void); </b>/*!< maximum compression level available */<b> 180int ZSTD_defaultCLevel(void); </b>/*!< default compression level, specified by ZSTD_CLEVEL_DEFAULT, requires v1.5.0+ */<b> 181</pre></b><BR> 182<a name="Chapter4"></a><h2>Explicit context</h2><pre></pre> 183 184<h3>Compression context</h3><pre> When compressing many times, 185 it is recommended to allocate a compression context just once, 186 and reuse it for each successive compression operation. 187 This will make the workload easier for system's memory. 188 Note : re-using context is just a speed / resource optimization. 189 It doesn't change the compression ratio, which remains identical. 190 Note 2: For parallel execution in multi-threaded environments, 191 use one different context per thread . 192 193</pre><b><pre>typedef struct ZSTD_CCtx_s ZSTD_CCtx; 194ZSTD_CCtx* ZSTD_createCCtx(void); 195size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx); </b>/* compatible with NULL pointer */<b> 196</pre></b><BR> 197<pre><b>size_t ZSTD_compressCCtx(ZSTD_CCtx* cctx, 198 void* dst, size_t dstCapacity, 199 const void* src, size_t srcSize, 200 int compressionLevel); 201</b><p> Same as ZSTD_compress(), using an explicit ZSTD_CCtx. 202 Important : in order to mirror `ZSTD_compress()` behavior, 203 this function compresses at the requested compression level, 204 __ignoring any other advanced parameter__ . 205 If any advanced parameter was set using the advanced API, 206 they will all be reset. Only @compressionLevel remains. 207 208</p></pre><BR> 209 210<h3>Decompression context</h3><pre> When decompressing many times, 211 it is recommended to allocate a context only once, 212 and reuse it for each successive compression operation. 213 This will make workload friendlier for system's memory. 214 Use one context per thread for parallel execution. 215</pre><b><pre>typedef struct ZSTD_DCtx_s ZSTD_DCtx; 216ZSTD_DCtx* ZSTD_createDCtx(void); 217size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx); </b>/* accept NULL pointer */<b> 218</pre></b><BR> 219<pre><b>size_t ZSTD_decompressDCtx(ZSTD_DCtx* dctx, 220 void* dst, size_t dstCapacity, 221 const void* src, size_t srcSize); 222</b><p> Same as ZSTD_decompress(), 223 requires an allocated ZSTD_DCtx. 224 Compatible with sticky parameters (see below). 225 226</p></pre><BR> 227 228<a name="Chapter5"></a><h2>Advanced compression API (Requires v1.4.0+)</h2><pre></pre> 229 230<pre><b>typedef enum { ZSTD_fast=1, 231 ZSTD_dfast=2, 232 ZSTD_greedy=3, 233 ZSTD_lazy=4, 234 ZSTD_lazy2=5, 235 ZSTD_btlazy2=6, 236 ZSTD_btopt=7, 237 ZSTD_btultra=8, 238 ZSTD_btultra2=9 239 </b>/* note : new strategies _might_ be added in the future.<b> 240 Only the order (from fast to strong) is guaranteed */ 241} ZSTD_strategy; 242</b></pre><BR> 243<pre><b>typedef enum { 244 245 </b>/* compression parameters<b> 246 * Note: When compressing with a ZSTD_CDict these parameters are superseded 247 * by the parameters used to construct the ZSTD_CDict. 248 * See ZSTD_CCtx_refCDict() for more info (superseded-by-cdict). */ 249 ZSTD_c_compressionLevel=100, </b>/* Set compression parameters according to pre-defined cLevel table.<b> 250 * Note that exact compression parameters are dynamically determined, 251 * depending on both compression level and srcSize (when known). 252 * Default level is ZSTD_CLEVEL_DEFAULT==3. 253 * Special: value 0 means default, which is controlled by ZSTD_CLEVEL_DEFAULT. 254 * Note 1 : it's possible to pass a negative compression level. 255 * Note 2 : setting a level does not automatically set all other compression parameters 256 * to default. Setting this will however eventually dynamically impact the compression 257 * parameters which have not been manually set. The manually set 258 * ones will 'stick'. */ 259 </b>/* Advanced compression parameters :<b> 260 * It's possible to pin down compression parameters to some specific values. 261 * In which case, these values are no longer dynamically selected by the compressor */ 262 ZSTD_c_windowLog=101, </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b> 263 * This will set a memory budget for streaming decompression, 264 * with larger values requiring more memory 265 * and typically compressing more. 266 * Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX. 267 * Special: value 0 means "use default windowLog". 268 * Note: Using a windowLog greater than ZSTD_WINDOWLOG_LIMIT_DEFAULT 269 * requires explicitly allowing such size at streaming decompression stage. */ 270 ZSTD_c_hashLog=102, </b>/* Size of the initial probe table, as a power of 2.<b> 271 * Resulting memory usage is (1 << (hashLog+2)). 272 * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX. 273 * Larger tables improve compression ratio of strategies <= dFast, 274 * and improve speed of strategies > dFast. 275 * Special: value 0 means "use default hashLog". */ 276 ZSTD_c_chainLog=103, </b>/* Size of the multi-probe search table, as a power of 2.<b> 277 * Resulting memory usage is (1 << (chainLog+2)). 278 * Must be clamped between ZSTD_CHAINLOG_MIN and ZSTD_CHAINLOG_MAX. 279 * Larger tables result in better and slower compression. 280 * This parameter is useless for "fast" strategy. 281 * It's still useful when using "dfast" strategy, 282 * in which case it defines a secondary probe table. 283 * Special: value 0 means "use default chainLog". */ 284 ZSTD_c_searchLog=104, </b>/* Number of search attempts, as a power of 2.<b> 285 * More attempts result in better and slower compression. 286 * This parameter is useless for "fast" and "dFast" strategies. 287 * Special: value 0 means "use default searchLog". */ 288 ZSTD_c_minMatch=105, </b>/* Minimum size of searched matches.<b> 289 * Note that Zstandard can still find matches of smaller size, 290 * it just tweaks its search algorithm to look for this size and larger. 291 * Larger values increase compression and decompression speed, but decrease ratio. 292 * Must be clamped between ZSTD_MINMATCH_MIN and ZSTD_MINMATCH_MAX. 293 * Note that currently, for all strategies < btopt, effective minimum is 4. 294 * , for all strategies > fast, effective maximum is 6. 295 * Special: value 0 means "use default minMatchLength". */ 296 ZSTD_c_targetLength=106, </b>/* Impact of this field depends on strategy.<b> 297 * For strategies btopt, btultra & btultra2: 298 * Length of Match considered "good enough" to stop search. 299 * Larger values make compression stronger, and slower. 300 * For strategy fast: 301 * Distance between match sampling. 302 * Larger values make compression faster, and weaker. 303 * Special: value 0 means "use default targetLength". */ 304 ZSTD_c_strategy=107, </b>/* See ZSTD_strategy enum definition.<b> 305 * The higher the value of selected strategy, the more complex it is, 306 * resulting in stronger and slower compression. 307 * Special: value 0 means "use default strategy". */ 308 309 ZSTD_c_targetCBlockSize=130, </b>/* v1.5.6+<b> 310 * Attempts to fit compressed block size into approximately targetCBlockSize. 311 * Bound by ZSTD_TARGETCBLOCKSIZE_MIN and ZSTD_TARGETCBLOCKSIZE_MAX. 312 * Note that it's not a guarantee, just a convergence target (default:0). 313 * No target when targetCBlockSize == 0. 314 * This is helpful in low bandwidth streaming environments to improve end-to-end latency, 315 * when a client can make use of partial documents (a prominent example being Chrome). 316 * Note: this parameter is stable since v1.5.6. 317 * It was present as an experimental parameter in earlier versions, 318 * but it's not recommended using it with earlier library versions 319 * due to massive performance regressions. 320 */ 321 </b>/* LDM mode parameters */<b> 322 ZSTD_c_enableLongDistanceMatching=160, </b>/* Enable long distance matching.<b> 323 * This parameter is designed to improve compression ratio 324 * for large inputs, by finding large matches at long distance. 325 * It increases memory usage and window size. 326 * Note: enabling this parameter increases default ZSTD_c_windowLog to 128 MB 327 * except when expressly set to a different value. 328 * Note: will be enabled by default if ZSTD_c_windowLog >= 128 MB and 329 * compression strategy >= ZSTD_btopt (== compression level 16+) */ 330 ZSTD_c_ldmHashLog=161, </b>/* Size of the table for long distance matching, as a power of 2.<b> 331 * Larger values increase memory usage and compression ratio, 332 * but decrease compression speed. 333 * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX 334 * default: windowlog - 7. 335 * Special: value 0 means "automatically determine hashlog". */ 336 ZSTD_c_ldmMinMatch=162, </b>/* Minimum match size for long distance matcher.<b> 337 * Larger/too small values usually decrease compression ratio. 338 * Must be clamped between ZSTD_LDM_MINMATCH_MIN and ZSTD_LDM_MINMATCH_MAX. 339 * Special: value 0 means "use default value" (default: 64). */ 340 ZSTD_c_ldmBucketSizeLog=163, </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b> 341 * Larger values improve collision resolution but decrease compression speed. 342 * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX. 343 * Special: value 0 means "use default value" (default: 3). */ 344 ZSTD_c_ldmHashRateLog=164, </b>/* Frequency of inserting/looking up entries into the LDM hash table.<b> 345 * Must be clamped between 0 and (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN). 346 * Default is MAX(0, (windowLog - ldmHashLog)), optimizing hash table usage. 347 * Larger values improve compression speed. 348 * Deviating far from default value will likely result in a compression ratio decrease. 349 * Special: value 0 means "automatically determine hashRateLog". */ 350 351 </b>/* frame parameters */<b> 352 ZSTD_c_contentSizeFlag=200, </b>/* Content size will be written into frame header _whenever known_ (default:1)<b> 353 * Content size must be known at the beginning of compression. 354 * This is automatically the case when using ZSTD_compress2(), 355 * For streaming scenarios, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */ 356 ZSTD_c_checksumFlag=201, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b> 357 ZSTD_c_dictIDFlag=202, </b>/* When applicable, dictionary's ID is written into frame header (default:1) */<b> 358 359 </b>/* multi-threading parameters */<b> 360 </b>/* These parameters are only active if multi-threading is enabled (compiled with build macro ZSTD_MULTITHREAD).<b> 361 * Otherwise, trying to set any other value than default (0) will be a no-op and return an error. 362 * In a situation where it's unknown if the linked library supports multi-threading or not, 363 * setting ZSTD_c_nbWorkers to any value >= 1 and consulting the return value provides a quick way to check this property. 364 */ 365 ZSTD_c_nbWorkers=400, </b>/* Select how many threads will be spawned to compress in parallel.<b> 366 * When nbWorkers >= 1, triggers asynchronous mode when invoking ZSTD_compressStream*() : 367 * ZSTD_compressStream*() consumes input and flush output if possible, but immediately gives back control to caller, 368 * while compression is performed in parallel, within worker thread(s). 369 * (note : a strong exception to this rule is when first invocation of ZSTD_compressStream2() sets ZSTD_e_end : 370 * in which case, ZSTD_compressStream2() delegates to ZSTD_compress2(), which is always a blocking call). 371 * More workers improve speed, but also increase memory usage. 372 * Default value is `0`, aka "single-threaded mode" : no worker is spawned, 373 * compression is performed inside Caller's thread, and all invocations are blocking */ 374 ZSTD_c_jobSize=401, </b>/* Size of a compression job. This value is enforced only when nbWorkers >= 1.<b> 375 * Each compression job is completed in parallel, so this value can indirectly impact the nb of active threads. 376 * 0 means default, which is dynamically determined based on compression parameters. 377 * Job size must be a minimum of overlap size, or ZSTDMT_JOBSIZE_MIN (= 512 KB), whichever is largest. 378 * The minimum size is automatically and transparently enforced. */ 379 ZSTD_c_overlapLog=402, </b>/* Control the overlap size, as a fraction of window size.<b> 380 * The overlap size is an amount of data reloaded from previous job at the beginning of a new job. 381 * It helps preserve compression ratio, while each job is compressed in parallel. 382 * This value is enforced only when nbWorkers >= 1. 383 * Larger values increase compression ratio, but decrease speed. 384 * Possible values range from 0 to 9 : 385 * - 0 means "default" : value will be determined by the library, depending on strategy 386 * - 1 means "no overlap" 387 * - 9 means "full overlap", using a full window size. 388 * Each intermediate rank increases/decreases load size by a factor 2 : 389 * 9: full window; 8: w/2; 7: w/4; 6: w/8; 5:w/16; 4: w/32; 3:w/64; 2:w/128; 1:no overlap; 0:default 390 * default value varies between 6 and 9, depending on strategy */ 391 392 </b>/* note : additional experimental parameters are also available<b> 393 * within the experimental section of the API. 394 * At the time of this writing, they include : 395 * ZSTD_c_rsyncable 396 * ZSTD_c_format 397 * ZSTD_c_forceMaxWindow 398 * ZSTD_c_forceAttachDict 399 * ZSTD_c_literalCompressionMode 400 * ZSTD_c_srcSizeHint 401 * ZSTD_c_enableDedicatedDictSearch 402 * ZSTD_c_stableInBuffer 403 * ZSTD_c_stableOutBuffer 404 * ZSTD_c_blockDelimiters 405 * ZSTD_c_validateSequences 406 * ZSTD_c_blockSplitterLevel 407 * ZSTD_c_splitAfterSequences 408 * ZSTD_c_useRowMatchFinder 409 * ZSTD_c_prefetchCDictTables 410 * ZSTD_c_enableSeqProducerFallback 411 * ZSTD_c_maxBlockSize 412 * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them. 413 * note : never ever use experimentalParam? names directly; 414 * also, the enums values themselves are unstable and can still change. 415 */ 416 ZSTD_c_experimentalParam1=500, 417 ZSTD_c_experimentalParam2=10, 418 ZSTD_c_experimentalParam3=1000, 419 ZSTD_c_experimentalParam4=1001, 420 ZSTD_c_experimentalParam5=1002, 421 </b>/* was ZSTD_c_experimentalParam6=1003; is now ZSTD_c_targetCBlockSize */<b> 422 ZSTD_c_experimentalParam7=1004, 423 ZSTD_c_experimentalParam8=1005, 424 ZSTD_c_experimentalParam9=1006, 425 ZSTD_c_experimentalParam10=1007, 426 ZSTD_c_experimentalParam11=1008, 427 ZSTD_c_experimentalParam12=1009, 428 ZSTD_c_experimentalParam13=1010, 429 ZSTD_c_experimentalParam14=1011, 430 ZSTD_c_experimentalParam15=1012, 431 ZSTD_c_experimentalParam16=1013, 432 ZSTD_c_experimentalParam17=1014, 433 ZSTD_c_experimentalParam18=1015, 434 ZSTD_c_experimentalParam19=1016, 435 ZSTD_c_experimentalParam20=1017 436} ZSTD_cParameter; 437</b></pre><BR> 438<pre><b>typedef struct { 439 size_t error; 440 int lowerBound; 441 int upperBound; 442} ZSTD_bounds; 443</b></pre><BR> 444<pre><b>ZSTD_bounds ZSTD_cParam_getBounds(ZSTD_cParameter cParam); 445</b><p> All parameters must belong to an interval with lower and upper bounds, 446 otherwise they will either trigger an error or be automatically clamped. 447 @return : a structure, ZSTD_bounds, which contains 448 - an error status field, which must be tested using ZSTD_isError() 449 - lower and upper bounds, both inclusive 450 451</p></pre><BR> 452 453<pre><b>size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value); 454</b><p> Set one compression parameter, selected by enum ZSTD_cParameter. 455 All parameters have valid bounds. Bounds can be queried using ZSTD_cParam_getBounds(). 456 Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter). 457 Setting a parameter is generally only possible during frame initialization (before starting compression). 458 Exception : when using multi-threading mode (nbWorkers >= 1), 459 the following parameters can be updated _during_ compression (within same frame): 460 => compressionLevel, hashLog, chainLog, searchLog, minMatch, targetLength and strategy. 461 new parameters will be active for next job only (after a flush()). 462 @return : an error code (which can be tested using ZSTD_isError()). 463 464</p></pre><BR> 465 466<pre><b>size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize); 467</b><p> Total input data size to be compressed as a single frame. 468 Value will be written in frame header, unless if explicitly forbidden using ZSTD_c_contentSizeFlag. 469 This value will also be controlled at end of frame, and trigger an error if not respected. 470 @result : 0, or an error code (which can be tested with ZSTD_isError()). 471 Note 1 : pledgedSrcSize==0 actually means zero, aka an empty frame. 472 In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN. 473 ZSTD_CONTENTSIZE_UNKNOWN is default value for any new frame. 474 Note 2 : pledgedSrcSize is only valid once, for the next frame. 475 It's discarded at the end of the frame, and replaced by ZSTD_CONTENTSIZE_UNKNOWN. 476 Note 3 : Whenever all input data is provided and consumed in a single round, 477 for example with ZSTD_compress2(), 478 or invoking immediately ZSTD_compressStream2(,,,ZSTD_e_end), 479 this value is automatically overridden by srcSize instead. 480 481</p></pre><BR> 482 483<pre><b>typedef enum { 484 ZSTD_reset_session_only = 1, 485 ZSTD_reset_parameters = 2, 486 ZSTD_reset_session_and_parameters = 3 487} ZSTD_ResetDirective; 488</b></pre><BR> 489<pre><b>size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx, ZSTD_ResetDirective reset); 490</b><p> There are 2 different things that can be reset, independently or jointly : 491 - The session : will stop compressing current frame, and make CCtx ready to start a new one. 492 Useful after an error, or to interrupt any ongoing compression. 493 Any internal data not yet flushed is cancelled. 494 Compression parameters and dictionary remain unchanged. 495 They will be used to compress next frame. 496 Resetting session never fails. 497 - The parameters : changes all parameters back to "default". 498 This also removes any reference to any dictionary or external sequence producer. 499 Parameters can only be changed between 2 sessions (i.e. no compression is currently ongoing) 500 otherwise the reset fails, and function returns an error value (which can be tested using ZSTD_isError()) 501 - Both : similar to resetting the session, followed by resetting parameters. 502 503</p></pre><BR> 504 505<pre><b>size_t ZSTD_compress2( ZSTD_CCtx* cctx, 506 void* dst, size_t dstCapacity, 507 const void* src, size_t srcSize); 508</b><p> Behave the same as ZSTD_compressCCtx(), but compression parameters are set using the advanced API. 509 (note that this entry point doesn't even expose a compression level parameter). 510 ZSTD_compress2() always starts a new frame. 511 Should cctx hold data from a previously unfinished frame, everything about it is forgotten. 512 - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*() 513 - The function is always blocking, returns when compression is completed. 514 NOTE: Providing `dstCapacity >= ZSTD_compressBound(srcSize)` guarantees that zstd will have 515 enough space to successfully compress the data, though it is possible it fails for other reasons. 516 @return : compressed size written into `dst` (<= `dstCapacity), 517 or an error code if it fails (which can be tested using ZSTD_isError()). 518 519</p></pre><BR> 520 521<a name="Chapter6"></a><h2>Advanced decompression API (Requires v1.4.0+)</h2><pre></pre> 522 523<pre><b>typedef enum { 524 525 ZSTD_d_windowLogMax=100, </b>/* Select a size limit (in power of 2) beyond which<b> 526 * the streaming API will refuse to allocate memory buffer 527 * in order to protect the host from unreasonable memory requirements. 528 * This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode. 529 * By default, a decompression context accepts window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT). 530 * Special: value 0 means "use default maximum windowLog". */ 531 532 </b>/* note : additional experimental parameters are also available<b> 533 * within the experimental section of the API. 534 * At the time of this writing, they include : 535 * ZSTD_d_format 536 * ZSTD_d_stableOutBuffer 537 * ZSTD_d_forceIgnoreChecksum 538 * ZSTD_d_refMultipleDDicts 539 * ZSTD_d_disableHuffmanAssembly 540 * ZSTD_d_maxBlockSize 541 * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them. 542 * note : never ever use experimentalParam? names directly 543 */ 544 ZSTD_d_experimentalParam1=1000, 545 ZSTD_d_experimentalParam2=1001, 546 ZSTD_d_experimentalParam3=1002, 547 ZSTD_d_experimentalParam4=1003, 548 ZSTD_d_experimentalParam5=1004, 549 ZSTD_d_experimentalParam6=1005 550 551} ZSTD_dParameter; 552</b></pre><BR> 553<pre><b>ZSTD_bounds ZSTD_dParam_getBounds(ZSTD_dParameter dParam); 554</b><p> All parameters must belong to an interval with lower and upper bounds, 555 otherwise they will either trigger an error or be automatically clamped. 556 @return : a structure, ZSTD_bounds, which contains 557 - an error status field, which must be tested using ZSTD_isError() 558 - both lower and upper bounds, inclusive 559 560</p></pre><BR> 561 562<pre><b>size_t ZSTD_DCtx_setParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int value); 563</b><p> Set one compression parameter, selected by enum ZSTD_dParameter. 564 All parameters have valid bounds. Bounds can be queried using ZSTD_dParam_getBounds(). 565 Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter). 566 Setting a parameter is only possible during frame initialization (before starting decompression). 567 @return : 0, or an error code (which can be tested using ZSTD_isError()). 568 569</p></pre><BR> 570 571<pre><b>size_t ZSTD_DCtx_reset(ZSTD_DCtx* dctx, ZSTD_ResetDirective reset); 572</b><p> Return a DCtx to clean state. 573 Session and parameters can be reset jointly or separately. 574 Parameters can only be reset when no active frame is being decompressed. 575 @return : 0, or an error code, which can be tested with ZSTD_isError() 576 577</p></pre><BR> 578 579<a name="Chapter7"></a><h2>Streaming</h2><pre></pre> 580 581<pre><b>typedef struct ZSTD_inBuffer_s { 582 const void* src; </b>/**< start of input buffer */<b> 583 size_t size; </b>/**< size of input buffer */<b> 584 size_t pos; </b>/**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */<b> 585} ZSTD_inBuffer; 586</b></pre><BR> 587<pre><b>typedef struct ZSTD_outBuffer_s { 588 void* dst; </b>/**< start of output buffer */<b> 589 size_t size; </b>/**< size of output buffer */<b> 590 size_t pos; </b>/**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */<b> 591} ZSTD_outBuffer; 592</b></pre><BR> 593<a name="Chapter8"></a><h2>Streaming compression - HowTo</h2><pre> 594 A ZSTD_CStream object is required to track streaming operation. 595 Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources. 596 ZSTD_CStream objects can be reused multiple times on consecutive compression operations. 597 It is recommended to reuse ZSTD_CStream since it will play nicer with system's memory, by re-using already allocated memory. 598 599 For parallel execution, use one separate ZSTD_CStream per thread. 600 601 note : since v1.3.0, ZSTD_CStream and ZSTD_CCtx are the same thing. 602 603 Parameters are sticky : when starting a new compression on the same context, 604 it will reuse the same sticky parameters as previous compression session. 605 When in doubt, it's recommended to fully initialize the context before usage. 606 Use ZSTD_CCtx_reset() to reset the context and ZSTD_CCtx_setParameter(), 607 ZSTD_CCtx_setPledgedSrcSize(), or ZSTD_CCtx_loadDictionary() and friends to 608 set more specific parameters, the pledged source size, or load a dictionary. 609 610 Use ZSTD_compressStream2() with ZSTD_e_continue as many times as necessary to 611 consume input stream. The function will automatically update both `pos` 612 fields within `input` and `output`. 613 Note that the function may not consume the entire input, for example, because 614 the output buffer is already full, in which case `input.pos < input.size`. 615 The caller must check if input has been entirely consumed. 616 If not, the caller must make some room to receive more compressed data, 617 and then present again remaining input data. 618 note: ZSTD_e_continue is guaranteed to make some forward progress when called, 619 but doesn't guarantee maximal forward progress. This is especially relevant 620 when compressing with multiple threads. The call won't block if it can 621 consume some input, but if it can't it will wait for some, but not all, 622 output to be flushed. 623 @return : provides a minimum amount of data remaining to be flushed from internal buffers 624 or an error code, which can be tested using ZSTD_isError(). 625 626 At any moment, it's possible to flush whatever data might remain stuck within internal buffer, 627 using ZSTD_compressStream2() with ZSTD_e_flush. `output->pos` will be updated. 628 Note that, if `output->size` is too small, a single invocation with ZSTD_e_flush might not be enough (return code > 0). 629 In which case, make some room to receive more compressed data, and call again ZSTD_compressStream2() with ZSTD_e_flush. 630 You must continue calling ZSTD_compressStream2() with ZSTD_e_flush until it returns 0, at which point you can change the 631 operation. 632 note: ZSTD_e_flush will flush as much output as possible, meaning when compressing with multiple threads, it will 633 block until the flush is complete or the output buffer is full. 634 @return : 0 if internal buffers are entirely flushed, 635 >0 if some data still present within internal buffer (the value is minimal estimation of remaining size), 636 or an error code, which can be tested using ZSTD_isError(). 637 638 Calling ZSTD_compressStream2() with ZSTD_e_end instructs to finish a frame. 639 It will perform a flush and write frame epilogue. 640 The epilogue is required for decoders to consider a frame completed. 641 flush operation is the same, and follows same rules as calling ZSTD_compressStream2() with ZSTD_e_flush. 642 You must continue calling ZSTD_compressStream2() with ZSTD_e_end until it returns 0, at which point you are free to 643 start a new frame. 644 note: ZSTD_e_end will flush as much output as possible, meaning when compressing with multiple threads, it will 645 block until the flush is complete or the output buffer is full. 646 @return : 0 if frame fully completed and fully flushed, 647 >0 if some data still present within internal buffer (the value is minimal estimation of remaining size), 648 or an error code, which can be tested using ZSTD_isError(). 649 650 651<BR></pre> 652 653<pre><b>typedef ZSTD_CCtx ZSTD_CStream; </b>/**< CCtx and CStream are now effectively same object (>= v1.3.0) */<b> 654</b></pre><BR> 655<h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void); 656size_t ZSTD_freeCStream(ZSTD_CStream* zcs); </b>/* accept NULL pointer */<b> 657</pre></b><BR> 658<h3>Streaming compression functions</h3><pre></pre><b><pre>typedef enum { 659 ZSTD_e_continue=0, </b>/* collect more data, encoder decides when to output compressed result, for optimal compression ratio */<b> 660 ZSTD_e_flush=1, </b>/* flush any data provided so far,<b> 661 * it creates (at least) one new block, that can be decoded immediately on reception; 662 * frame will continue: any future data can still reference previously compressed data, improving compression. 663 * note : multithreaded compression will block to flush as much output as possible. */ 664 ZSTD_e_end=2 </b>/* flush any remaining data _and_ close current frame.<b> 665 * note that frame is only closed after compressed data is fully flushed (return value == 0). 666 * After that point, any additional data starts a new frame. 667 * note : each frame is independent (does not reference any content from previous frame). 668 : note : multithreaded compression will block to flush as much output as possible. */ 669} ZSTD_EndDirective; 670</pre></b><BR> 671<pre><b>size_t ZSTD_compressStream2( ZSTD_CCtx* cctx, 672 ZSTD_outBuffer* output, 673 ZSTD_inBuffer* input, 674 ZSTD_EndDirective endOp); 675</b><p> Behaves about the same as ZSTD_compressStream, with additional control on end directive. 676 - Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*() 677 - Compression parameters cannot be changed once compression is started (save a list of exceptions in multi-threading mode) 678 - output->pos must be <= dstCapacity, input->pos must be <= srcSize 679 - output->pos and input->pos will be updated. They are guaranteed to remain below their respective limit. 680 - endOp must be a valid directive 681 - When nbWorkers==0 (default), function is blocking : it completes its job before returning to caller. 682 - When nbWorkers>=1, function is non-blocking : it copies a portion of input, distributes jobs to internal worker threads, flush to output whatever is available, 683 and then immediately returns, just indicating that there is some data remaining to be flushed. 684 The function nonetheless guarantees forward progress : it will return only after it reads or write at least 1+ byte. 685 - Exception : if the first call requests a ZSTD_e_end directive and provides enough dstCapacity, the function delegates to ZSTD_compress2() which is always blocking. 686 - @return provides a minimum amount of data remaining to be flushed from internal buffers 687 or an error code, which can be tested using ZSTD_isError(). 688 if @return != 0, flush is not fully completed, there is still some data left within internal buffers. 689 This is useful for ZSTD_e_flush, since in this case more flushes are necessary to empty all buffers. 690 For ZSTD_e_end, @return == 0 when internal buffers are fully flushed and frame is completed. 691 - after a ZSTD_e_end directive, if internal buffer is not fully flushed (@return != 0), 692 only ZSTD_e_end or ZSTD_e_flush operations are allowed. 693 Before starting a new compression job, or changing compression parameters, 694 it is required to fully flush internal buffers. 695 - note: if an operation ends with an error, it may leave @cctx in an undefined state. 696 Therefore, it's UB to invoke ZSTD_compressStream2() of ZSTD_compressStream() on such a state. 697 In order to be re-employed after an error, a state must be reset, 698 which can be done explicitly (ZSTD_CCtx_reset()), 699 or is sometimes implied by methods starting a new compression job (ZSTD_initCStream(), ZSTD_compressCCtx()) 700 701</p></pre><BR> 702 703<pre><b>size_t ZSTD_CStreamInSize(void); </b>/**< recommended size for input buffer */<b> 704</b></pre><BR> 705<pre><b>size_t ZSTD_CStreamOutSize(void); </b>/**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block. */<b> 706</b></pre><BR> 707<pre><b>size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel); 708</b>/*!<b> 709 * Alternative for ZSTD_compressStream2(zcs, output, input, ZSTD_e_continue). 710 * NOTE: The return value is different. ZSTD_compressStream() returns a hint for 711 * the next read size (if non-zero and not an error). ZSTD_compressStream2() 712 * returns the minimum nb of bytes left to flush (if non-zero and not an error). 713 */ 714size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input); 715</b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_flush). */<b> 716size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output); 717</b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_end). */<b> 718size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output); 719</b><p> 720 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); 721 ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any) 722 ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel); 723 724 Note that ZSTD_initCStream() clears any previously set dictionary. Use the new API 725 to compress with a dictionary. 726 727</p></pre><BR> 728 729<a name="Chapter9"></a><h2>Streaming decompression - HowTo</h2><pre> 730 A ZSTD_DStream object is required to track streaming operations. 731 Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources. 732 ZSTD_DStream objects can be re-employed multiple times. 733 734 Use ZSTD_initDStream() to start a new decompression operation. 735 @return : recommended first input size 736 Alternatively, use advanced API to set specific properties. 737 738 Use ZSTD_decompressStream() repetitively to consume your input. 739 The function will update both `pos` fields. 740 If `input.pos < input.size`, some input has not been consumed. 741 It's up to the caller to present again remaining data. 742 743 The function tries to flush all data decoded immediately, respecting output buffer size. 744 If `output.pos < output.size`, decoder has flushed everything it could. 745 746 However, when `output.pos == output.size`, it's more difficult to know. 747 If @return > 0, the frame is not complete, meaning 748 either there is still some data left to flush within internal buffers, 749 or there is more input to read to complete the frame (or both). 750 In which case, call ZSTD_decompressStream() again to flush whatever remains in the buffer. 751 Note : with no additional input provided, amount of data flushed is necessarily <= ZSTD_BLOCKSIZE_MAX. 752 @return : 0 when a frame is completely decoded and fully flushed, 753 or an error code, which can be tested using ZSTD_isError(), 754 or any other value > 0, which means there is still some decoding or flushing to do to complete current frame : 755 the return value is a suggested next input size (just a hint for better latency) 756 that will never request more than the remaining content of the compressed frame. 757 758<BR></pre> 759 760<pre><b>typedef ZSTD_DCtx ZSTD_DStream; </b>/**< DCtx and DStream are now effectively same object (>= v1.3.0) */<b> 761</b></pre><BR> 762<h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void); 763size_t ZSTD_freeDStream(ZSTD_DStream* zds); </b>/* accept NULL pointer */<b> 764</pre></b><BR> 765<h3>Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR> 766<pre><b>size_t ZSTD_initDStream(ZSTD_DStream* zds); 767</b><p> Initialize/reset DStream state for new decompression operation. 768 Call before new decompression operation using same DStream. 769 770 Note : This function is redundant with the advanced API and equivalent to: 771 ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); 772 ZSTD_DCtx_refDDict(zds, NULL); 773 774</p></pre><BR> 775 776<pre><b>size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input); 777</b><p> Streaming decompression function. 778 Call repetitively to consume full input updating it as necessary. 779 Function will update both input and output `pos` fields exposing current state via these fields: 780 - `input.pos < input.size`, some input remaining and caller should provide remaining input 781 on the next call. 782 - `output.pos < output.size`, decoder flushed internal output buffer. 783 - `output.pos == output.size`, unflushed data potentially present in the internal buffers, 784 check ZSTD_decompressStream() @return value, 785 if > 0, invoke it again to flush remaining data to output. 786 Note : with no additional input, amount of data flushed <= ZSTD_BLOCKSIZE_MAX. 787 788 @return : 0 when a frame is completely decoded and fully flushed, 789 or an error code, which can be tested using ZSTD_isError(), 790 or any other value > 0, which means there is some decoding or flushing to do to complete current frame. 791 792 Note: when an operation returns with an error code, the @zds state may be left in undefined state. 793 It's UB to invoke `ZSTD_decompressStream()` on such a state. 794 In order to re-use such a state, it must be first reset, 795 which can be done explicitly (`ZSTD_DCtx_reset()`), 796 or is implied for operations starting some new decompression job (`ZSTD_initDStream`, `ZSTD_decompressDCtx()`, `ZSTD_decompress_usingDict()`) 797 798</p></pre><BR> 799 800<pre><b>size_t ZSTD_DStreamInSize(void); </b>/*!< recommended size for input buffer */<b> 801</b></pre><BR> 802<pre><b>size_t ZSTD_DStreamOutSize(void); </b>/*!< recommended size for output buffer. Guarantee to successfully flush at least one complete block in all circumstances. */<b> 803</b></pre><BR> 804<a name="Chapter10"></a><h2>Simple dictionary API</h2><pre></pre> 805 806<pre><b>size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx, 807 void* dst, size_t dstCapacity, 808 const void* src, size_t srcSize, 809 const void* dict,size_t dictSize, 810 int compressionLevel); 811</b><p> Compression at an explicit compression level using a Dictionary. 812 A dictionary can be any arbitrary data segment (also called a prefix), 813 or a buffer with specified information (see zdict.h). 814 Note : This function loads the dictionary, resulting in significant startup delay. 815 It's intended for a dictionary used only once. 816 Note 2 : When `dict == NULL || dictSize < 8` no dictionary is used. 817</p></pre><BR> 818 819<pre><b>size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx, 820 void* dst, size_t dstCapacity, 821 const void* src, size_t srcSize, 822 const void* dict,size_t dictSize); 823</b><p> Decompression using a known Dictionary. 824 Dictionary must be identical to the one used during compression. 825 Note : This function loads the dictionary, resulting in significant startup delay. 826 It's intended for a dictionary used only once. 827 Note : When `dict == NULL || dictSize < 8` no dictionary is used. 828</p></pre><BR> 829 830<a name="Chapter11"></a><h2>Bulk processing dictionary API</h2><pre></pre> 831 832<pre><b>ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize, 833 int compressionLevel); 834</b><p> When compressing multiple messages or blocks using the same dictionary, 835 it's recommended to digest the dictionary only once, since it's a costly operation. 836 ZSTD_createCDict() will create a state from digesting a dictionary. 837 The resulting state can be used for future compression operations with very limited startup cost. 838 ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only. 839 @dictBuffer can be released after ZSTD_CDict creation, because its content is copied within CDict. 840 Note 1 : Consider experimental function `ZSTD_createCDict_byReference()` if you prefer to not duplicate @dictBuffer content. 841 Note 2 : A ZSTD_CDict can be created from an empty @dictBuffer, 842 in which case the only thing that it transports is the @compressionLevel. 843 This can be useful in a pipeline featuring ZSTD_compress_usingCDict() exclusively, 844 expecting a ZSTD_CDict parameter with any data, including those without a known dictionary. 845</p></pre><BR> 846 847<pre><b>size_t ZSTD_freeCDict(ZSTD_CDict* CDict); 848</b><p> Function frees memory allocated by ZSTD_createCDict(). 849 If a NULL pointer is passed, no operation is performed. 850</p></pre><BR> 851 852<pre><b>size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx, 853 void* dst, size_t dstCapacity, 854 const void* src, size_t srcSize, 855 const ZSTD_CDict* cdict); 856</b><p> Compression using a digested Dictionary. 857 Recommended when same dictionary is used multiple times. 858 Note : compression level is _decided at dictionary creation time_, 859 and frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no) 860</p></pre><BR> 861 862<pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize); 863</b><p> Create a digested dictionary, ready to start decompression operation without startup delay. 864 dictBuffer can be released after DDict creation, as its content is copied inside DDict. 865</p></pre><BR> 866 867<pre><b>size_t ZSTD_freeDDict(ZSTD_DDict* ddict); 868</b><p> Function frees memory allocated with ZSTD_createDDict() 869 If a NULL pointer is passed, no operation is performed. 870</p></pre><BR> 871 872<pre><b>size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx, 873 void* dst, size_t dstCapacity, 874 const void* src, size_t srcSize, 875 const ZSTD_DDict* ddict); 876</b><p> Decompression using a digested Dictionary. 877 Recommended when same dictionary is used multiple times. 878</p></pre><BR> 879 880<a name="Chapter12"></a><h2>Dictionary helper functions</h2><pre></pre> 881 882<pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize); 883</b><p> Provides the dictID stored within dictionary. 884 if @return == 0, the dictionary is not conformant with Zstandard specification. 885 It can still be loaded, but as a content-only dictionary. 886</p></pre><BR> 887 888<pre><b>unsigned ZSTD_getDictID_fromCDict(const ZSTD_CDict* cdict); 889</b><p> Provides the dictID of the dictionary loaded into `cdict`. 890 If @return == 0, the dictionary is not conformant to Zstandard specification, or empty. 891 Non-conformant dictionaries can still be loaded, but as content-only dictionaries. 892</p></pre><BR> 893 894<pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict); 895</b><p> Provides the dictID of the dictionary loaded into `ddict`. 896 If @return == 0, the dictionary is not conformant to Zstandard specification, or empty. 897 Non-conformant dictionaries can still be loaded, but as content-only dictionaries. 898</p></pre><BR> 899 900<pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize); 901</b><p> Provides the dictID required to decompressed the frame stored within `src`. 902 If @return == 0, the dictID could not be decoded. 903 This could for one of the following reasons : 904 - The frame does not require a dictionary to be decoded (most common case). 905 - The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden piece of information. 906 Note : this use case also happens when using a non-conformant dictionary. 907 - `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`). 908 - This is not a Zstandard frame. 909 When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code. 910</p></pre><BR> 911 912<a name="Chapter13"></a><h2>Advanced dictionary and prefix API (Requires v1.4.0+)</h2><pre> 913 This API allows dictionaries to be used with ZSTD_compress2(), 914 ZSTD_compressStream2(), and ZSTD_decompressDCtx(). 915 Dictionaries are sticky, they remain valid when same context is reused, 916 they only reset when the context is reset 917 with ZSTD_reset_parameters or ZSTD_reset_session_and_parameters. 918 In contrast, Prefixes are single-use. 919<BR></pre> 920 921<pre><b>size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize); 922</b><p> Create an internal CDict from `dict` buffer. 923 Decompression will have to use same dictionary. 924 @result : 0, or an error code (which can be tested with ZSTD_isError()). 925 Special: Loading a NULL (or 0-size) dictionary invalidates previous dictionary, 926 meaning "return to no-dictionary mode". 927 Note 1 : Dictionary is sticky, it will be used for all future compressed frames, 928 until parameters are reset, a new dictionary is loaded, or the dictionary 929 is explicitly invalidated by loading a NULL dictionary. 930 Note 2 : Loading a dictionary involves building tables. 931 It's also a CPU consuming operation, with non-negligible impact on latency. 932 Tables are dependent on compression parameters, and for this reason, 933 compression parameters can no longer be changed after loading a dictionary. 934 Note 3 :`dict` content will be copied internally. 935 Use experimental ZSTD_CCtx_loadDictionary_byReference() to reference content instead. 936 In such a case, dictionary buffer must outlive its users. 937 Note 4 : Use ZSTD_CCtx_loadDictionary_advanced() 938 to precisely select how dictionary content must be interpreted. 939 Note 5 : This method does not benefit from LDM (long distance mode). 940 If you want to employ LDM on some large dictionary content, 941 prefer employing ZSTD_CCtx_refPrefix() described below. 942 943</p></pre><BR> 944 945<pre><b>size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); 946</b><p> Reference a prepared dictionary, to be used for all future compressed frames. 947 Note that compression parameters are enforced from within CDict, 948 and supersede any compression parameter previously set within CCtx. 949 The parameters ignored are labelled as "superseded-by-cdict" in the ZSTD_cParameter enum docs. 950 The ignored parameters will be used again if the CCtx is returned to no-dictionary mode. 951 The dictionary will remain valid for future compressed frames using same CCtx. 952 @result : 0, or an error code (which can be tested with ZSTD_isError()). 953 Special : Referencing a NULL CDict means "return to no-dictionary mode". 954 Note 1 : Currently, only one dictionary can be managed. 955 Referencing a new dictionary effectively "discards" any previous one. 956 Note 2 : CDict is just referenced, its lifetime must outlive its usage within CCtx. 957</p></pre><BR> 958 959<pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx, 960 const void* prefix, size_t prefixSize); 961</b><p> Reference a prefix (single-usage dictionary) for next compressed frame. 962 A prefix is **only used once**. Tables are discarded at end of frame (ZSTD_e_end). 963 Decompression will need same prefix to properly regenerate data. 964 Compressing with a prefix is similar in outcome as performing a diff and compressing it, 965 but performs much faster, especially during decompression (compression speed is tunable with compression level). 966 This method is compatible with LDM (long distance mode). 967 @result : 0, or an error code (which can be tested with ZSTD_isError()). 968 Special: Adding any prefix (including NULL) invalidates any previous prefix or dictionary 969 Note 1 : Prefix buffer is referenced. It **must** outlive compression. 970 Its content must remain unmodified during compression. 971 Note 2 : If the intention is to diff some large src data blob with some prior version of itself, 972 ensure that the window size is large enough to contain the entire source. 973 See ZSTD_c_windowLog. 974 Note 3 : Referencing a prefix involves building tables, which are dependent on compression parameters. 975 It's a CPU consuming operation, with non-negligible impact on latency. 976 If there is a need to use the same prefix multiple times, consider loadDictionary instead. 977 Note 4 : By default, the prefix is interpreted as raw content (ZSTD_dct_rawContent). 978 Use experimental ZSTD_CCtx_refPrefix_advanced() to alter dictionary interpretation. 979</p></pre><BR> 980 981<pre><b>size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize); 982</b><p> Create an internal DDict from dict buffer, to be used to decompress all future frames. 983 The dictionary remains valid for all future frames, until explicitly invalidated, or 984 a new dictionary is loaded. 985 @result : 0, or an error code (which can be tested with ZSTD_isError()). 986 Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary, 987 meaning "return to no-dictionary mode". 988 Note 1 : Loading a dictionary involves building tables, 989 which has a non-negligible impact on CPU usage and latency. 990 It's recommended to "load once, use many times", to amortize the cost 991 Note 2 :`dict` content will be copied internally, so `dict` can be released after loading. 992 Use ZSTD_DCtx_loadDictionary_byReference() to reference dictionary content instead. 993 Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to take control of 994 how dictionary content is loaded and interpreted. 995 996</p></pre><BR> 997 998<pre><b>size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict); 999</b><p> Reference a prepared dictionary, to be used to decompress next frames. 1000 The dictionary remains active for decompression of future frames using same DCtx. 1001 1002 If called with ZSTD_d_refMultipleDDicts enabled, repeated calls of this function 1003 will store the DDict references in a table, and the DDict used for decompression 1004 will be determined at decompression time, as per the dict ID in the frame. 1005 The memory for the table is allocated on the first call to refDDict, and can be 1006 freed with ZSTD_freeDCtx(). 1007 1008 If called with ZSTD_d_refMultipleDDicts disabled (the default), only one dictionary 1009 will be managed, and referencing a dictionary effectively "discards" any previous one. 1010 1011 @result : 0, or an error code (which can be tested with ZSTD_isError()). 1012 Special: referencing a NULL DDict means "return to no-dictionary mode". 1013 Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx. 1014 1015</p></pre><BR> 1016 1017<pre><b>size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx, 1018 const void* prefix, size_t prefixSize); 1019</b><p> Reference a prefix (single-usage dictionary) to decompress next frame. 1020 This is the reverse operation of ZSTD_CCtx_refPrefix(), 1021 and must use the same prefix as the one used during compression. 1022 Prefix is **only used once**. Reference is discarded at end of frame. 1023 End of frame is reached when ZSTD_decompressStream() returns 0. 1024 @result : 0, or an error code (which can be tested with ZSTD_isError()). 1025 Note 1 : Adding any prefix (including NULL) invalidates any previously set prefix or dictionary 1026 Note 2 : Prefix buffer is referenced. It **must** outlive decompression. 1027 Prefix buffer must remain unmodified up to the end of frame, 1028 reached when ZSTD_decompressStream() returns 0. 1029 Note 3 : By default, the prefix is treated as raw content (ZSTD_dct_rawContent). 1030 Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode (Experimental section) 1031 Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost. 1032 A full dictionary is more costly, as it requires building tables. 1033 1034</p></pre><BR> 1035 1036<pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx); 1037size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx); 1038size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs); 1039size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds); 1040size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict); 1041size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict); 1042</b><p> These functions give the _current_ memory usage of selected object. 1043 Note that object memory usage can evolve (increase or decrease) over time. 1044</p></pre><BR> 1045 1046<a name="Chapter14"></a><h2>experimental API (static linking only)</h2><pre> 1047 The following symbols and constants 1048 are not planned to join "stable API" status in the near future. 1049 They can still change in future versions. 1050 Some of them are planned to remain in the static_only section indefinitely. 1051 Some of them might be removed in the future (especially when redundant with existing stable functions) 1052 1053<BR></pre> 1054 1055<pre><b>typedef struct { 1056 unsigned int offset; </b>/* The offset of the match. (NOT the same as the offset code)<b> 1057 * If offset == 0 and matchLength == 0, this sequence represents the last 1058 * literals in the block of litLength size. 1059 */ 1060 1061 unsigned int litLength; </b>/* Literal length of the sequence. */<b> 1062 unsigned int matchLength; </b>/* Match length of the sequence. */<b> 1063 1064 </b>/* Note: Users of this API may provide a sequence with matchLength == litLength == offset == 0.<b> 1065 * In this case, we will treat the sequence as a marker for a block boundary. 1066 */ 1067 1068 unsigned int rep; </b>/* Represents which repeat offset is represented by the field 'offset'.<b> 1069 * Ranges from [0, 3]. 1070 * 1071 * Repeat offsets are essentially previous offsets from previous sequences sorted in 1072 * recency order. For more detail, see doc/zstd_compression_format.md 1073 * 1074 * If rep == 0, then 'offset' does not contain a repeat offset. 1075 * If rep > 0: 1076 * If litLength != 0: 1077 * rep == 1 --> offset == repeat_offset_1 1078 * rep == 2 --> offset == repeat_offset_2 1079 * rep == 3 --> offset == repeat_offset_3 1080 * If litLength == 0: 1081 * rep == 1 --> offset == repeat_offset_2 1082 * rep == 2 --> offset == repeat_offset_3 1083 * rep == 3 --> offset == repeat_offset_1 - 1 1084 * 1085 * Note: This field is optional. ZSTD_generateSequences() will calculate the value of 1086 * 'rep', but repeat offsets do not necessarily need to be calculated from an external 1087 * sequence provider perspective. For example, ZSTD_compressSequences() does not 1088 * use this 'rep' field at all (as of now). 1089 */ 1090} ZSTD_Sequence; 1091</b></pre><BR> 1092<pre><b>typedef struct { 1093 unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b> 1094 unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b> 1095 unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b> 1096 unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b> 1097 unsigned minMatch; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b> 1098 unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b> 1099 ZSTD_strategy strategy; </b>/**< see ZSTD_strategy definition above */<b> 1100} ZSTD_compressionParameters; 1101</b></pre><BR> 1102<pre><b>typedef struct { 1103 int contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b> 1104 int checksumFlag; </b>/**< 1: generate a 32-bits checksum using XXH64 algorithm at end of frame, for error detection */<b> 1105 int noDictIDFlag; </b>/**< 1: no dictID will be saved into frame header (dictID is only useful for dictionary compression) */<b> 1106} ZSTD_frameParameters; 1107</b></pre><BR> 1108<pre><b>typedef struct { 1109 ZSTD_compressionParameters cParams; 1110 ZSTD_frameParameters fParams; 1111} ZSTD_parameters; 1112</b></pre><BR> 1113<pre><b>typedef enum { 1114 ZSTD_dct_auto = 0, </b>/* dictionary is "full" when starting with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */<b> 1115 ZSTD_dct_rawContent = 1, </b>/* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */<b> 1116 ZSTD_dct_fullDict = 2 </b>/* refuses to load a dictionary if it does not respect Zstandard's specification, starting with ZSTD_MAGIC_DICTIONARY */<b> 1117} ZSTD_dictContentType_e; 1118</b></pre><BR> 1119<pre><b>typedef enum { 1120 ZSTD_dlm_byCopy = 0, </b>/**< Copy dictionary content internally */<b> 1121 ZSTD_dlm_byRef = 1 </b>/**< Reference dictionary content -- the dictionary buffer must outlive its users. */<b> 1122} ZSTD_dictLoadMethod_e; 1123</b></pre><BR> 1124<pre><b>typedef enum { 1125 ZSTD_f_zstd1 = 0, </b>/* zstd frame format, specified in zstd_compression_format.md (default) */<b> 1126 ZSTD_f_zstd1_magicless = 1 </b>/* Variant of zstd frame format, without initial 4-bytes magic number.<b> 1127 * Useful to save 4 bytes per generated frame. 1128 * Decoder cannot recognise automatically this format, requiring this instruction. */ 1129} ZSTD_format_e; 1130</b></pre><BR> 1131<pre><b>typedef enum { 1132 </b>/* Note: this enum controls ZSTD_d_forceIgnoreChecksum */<b> 1133 ZSTD_d_validateChecksum = 0, 1134 ZSTD_d_ignoreChecksum = 1 1135} ZSTD_forceIgnoreChecksum_e; 1136</b></pre><BR> 1137<pre><b>typedef enum { 1138 </b>/* Note: this enum controls ZSTD_d_refMultipleDDicts */<b> 1139 ZSTD_rmd_refSingleDDict = 0, 1140 ZSTD_rmd_refMultipleDDicts = 1 1141} ZSTD_refMultipleDDicts_e; 1142</b></pre><BR> 1143<pre><b>typedef enum { 1144 </b>/* Note: this enum and the behavior it controls are effectively internal<b> 1145 * implementation details of the compressor. They are expected to continue 1146 * to evolve and should be considered only in the context of extremely 1147 * advanced performance tuning. 1148 * 1149 * Zstd currently supports the use of a CDict in three ways: 1150 * 1151 * - The contents of the CDict can be copied into the working context. This 1152 * means that the compression can search both the dictionary and input 1153 * while operating on a single set of internal tables. This makes 1154 * the compression faster per-byte of input. However, the initial copy of 1155 * the CDict's tables incurs a fixed cost at the beginning of the 1156 * compression. For small compressions (< 8 KB), that copy can dominate 1157 * the cost of the compression. 1158 * 1159 * - The CDict's tables can be used in-place. In this model, compression is 1160 * slower per input byte, because the compressor has to search two sets of 1161 * tables. However, this model incurs no start-up cost (as long as the 1162 * working context's tables can be reused). For small inputs, this can be 1163 * faster than copying the CDict's tables. 1164 * 1165 * - The CDict's tables are not used at all, and instead we use the working 1166 * context alone to reload the dictionary and use params based on the source 1167 * size. See ZSTD_compress_insertDictionary() and ZSTD_compress_usingDict(). 1168 * This method is effective when the dictionary sizes are very small relative 1169 * to the input size, and the input size is fairly large to begin with. 1170 * 1171 * Zstd has a simple internal heuristic that selects which strategy to use 1172 * at the beginning of a compression. However, if experimentation shows that 1173 * Zstd is making poor choices, it is possible to override that choice with 1174 * this enum. 1175 */ 1176 ZSTD_dictDefaultAttach = 0, </b>/* Use the default heuristic. */<b> 1177 ZSTD_dictForceAttach = 1, </b>/* Never copy the dictionary. */<b> 1178 ZSTD_dictForceCopy = 2, </b>/* Always copy the dictionary. */<b> 1179 ZSTD_dictForceLoad = 3 </b>/* Always reload the dictionary */<b> 1180} ZSTD_dictAttachPref_e; 1181</b></pre><BR> 1182<pre><b>typedef enum { 1183 ZSTD_lcm_auto = 0, </b>/**< Automatically determine the compression mode based on the compression level.<b> 1184 * Negative compression levels will be uncompressed, and positive compression 1185 * levels will be compressed. */ 1186 ZSTD_lcm_huffman = 1, </b>/**< Always attempt Huffman compression. Uncompressed literals will still be<b> 1187 * emitted if Huffman compression is not profitable. */ 1188 ZSTD_lcm_uncompressed = 2 </b>/**< Always emit uncompressed literals. */<b> 1189} ZSTD_literalCompressionMode_e; 1190</b></pre><BR> 1191<pre><b>typedef enum { 1192 </b>/* Note: This enum controls features which are conditionally beneficial.<b> 1193 * Zstd can take a decision on whether or not to enable the feature (ZSTD_ps_auto), 1194 * but setting the switch to ZSTD_ps_enable or ZSTD_ps_disable force enable/disable the feature. 1195 */ 1196 ZSTD_ps_auto = 0, </b>/* Let the library automatically determine whether the feature shall be enabled */<b> 1197 ZSTD_ps_enable = 1, </b>/* Force-enable the feature */<b> 1198 ZSTD_ps_disable = 2 </b>/* Do not use the feature */<b> 1199} ZSTD_ParamSwitch_e; 1200</b></pre><BR> 1201<a name="Chapter15"></a><h2>Frame header and size functions</h2><pre></pre> 1202 1203<pre><b>ZSTDLIB_STATIC_API unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize); 1204</b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames 1205 `srcSize` must be the _exact_ size of this series 1206 (i.e. there should be a frame boundary at `src + srcSize`) 1207 @return : - decompressed size of all data in all successive frames 1208 - if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN 1209 - if an error occurred: ZSTD_CONTENTSIZE_ERROR 1210 1211 note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode. 1212 When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size. 1213 In which case, it's necessary to use streaming mode to decompress data. 1214 note 2 : decompressed size is always present when compression is done with ZSTD_compress() 1215 note 3 : decompressed size can be very large (64-bits value), 1216 potentially larger than what local system can handle as a single memory segment. 1217 In which case, it's necessary to use streaming mode to decompress data. 1218 note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified. 1219 Always ensure result fits within application's authorized limits. 1220 Each application can set its own limits. 1221 note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to 1222 read each contained frame header. This is fast as most of the data is skipped, 1223 however it does mean that all frame data must be present and valid. 1224</p></pre><BR> 1225 1226<pre><b>ZSTDLIB_STATIC_API unsigned long long ZSTD_decompressBound(const void* src, size_t srcSize); 1227</b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames 1228 `srcSize` must be the _exact_ size of this series 1229 (i.e. there should be a frame boundary at `src + srcSize`) 1230 @return : - upper-bound for the decompressed size of all data in all successive frames 1231 - if an error occurred: ZSTD_CONTENTSIZE_ERROR 1232 1233 note 1 : an error can occur if `src` contains an invalid or incorrectly formatted frame. 1234 note 2 : the upper-bound is exact when the decompressed size field is available in every ZSTD encoded frame of `src`. 1235 in this case, `ZSTD_findDecompressedSize` and `ZSTD_decompressBound` return the same value. 1236 note 3 : when the decompressed size field isn't available, the upper-bound for that frame is calculated by: 1237 upper-bound = # blocks * min(128 KB, Window_Size) 1238 1239</p></pre><BR> 1240 1241<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize); 1242</b><p> srcSize must be >= ZSTD_FRAMEHEADERSIZE_PREFIX. 1243 @return : size of the Frame Header, 1244 or an error code (if srcSize is too small) 1245</p></pre><BR> 1246 1247<pre><b>typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_FrameType_e; 1248</b></pre><BR> 1249<pre><b>typedef struct { 1250 unsigned long long frameContentSize; </b>/* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */<b> 1251 unsigned long long windowSize; </b>/* can be very large, up to <= frameContentSize */<b> 1252 unsigned blockSizeMax; 1253 ZSTD_FrameType_e frameType; </b>/* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */<b> 1254 unsigned headerSize; 1255 unsigned dictID; 1256 unsigned checksumFlag; 1257 unsigned _reserved1; 1258 unsigned _reserved2; 1259} ZSTD_frameHeader; 1260</b></pre><BR> 1261<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_getFrameHeader(ZSTD_FrameHeader* zfhPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input */<b> 1262</b>/*! ZSTD_getFrameHeader_advanced() :<b> 1263 * same as ZSTD_getFrameHeader(), 1264 * with added capability to select a format (like ZSTD_f_zstd1_magicless) */ 1265ZSTDLIB_STATIC_API size_t ZSTD_getFrameHeader_advanced(ZSTD_FrameHeader* zfhPtr, const void* src, size_t srcSize, ZSTD_format_e format); 1266</b><p> decode Frame Header, or requires larger `srcSize`. 1267 @return : 0, `zfhPtr` is correctly filled, 1268 >0, `srcSize` is too small, value is wanted `srcSize` amount, 1269 or an error code, which can be tested using ZSTD_isError() 1270</p></pre><BR> 1271 1272<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decompressionMargin(const void* src, size_t srcSize); 1273</b><p> Zstd supports in-place decompression, where the input and output buffers overlap. 1274 In this case, the output buffer must be at least (Margin + Output_Size) bytes large, 1275 and the input buffer must be at the end of the output buffer. 1276 1277 _______________________ Output Buffer ________________________ 1278 | | 1279 | ____ Input Buffer ____| 1280 | | | 1281 v v v 1282 |---------------------------------------|-----------|----------| 1283 ^ ^ ^ 1284 |___________________ Output_Size ___________________|_ Margin _| 1285 1286 NOTE: See also ZSTD_DECOMPRESSION_MARGIN(). 1287 NOTE: This applies only to single-pass decompression through ZSTD_decompress() or 1288 ZSTD_decompressDCtx(). 1289 NOTE: This function supports multi-frame input. 1290 1291 @param src The compressed frame(s) 1292 @param srcSize The size of the compressed frame(s) 1293 @returns The decompression margin or an error that can be checked with ZSTD_isError(). 1294 1295</p></pre><BR> 1296 1297<pre><b>#define ZSTD_DECOMPRESSION_MARGIN(originalSize, blockSize) ((size_t)( \ 1298 ZSTD_FRAMEHEADERSIZE_MAX </b>/* Frame header */ + \<b> 1299 4 </b>/* checksum */ + \<b> 1300 ((originalSize) == 0 ? 0 : 3 * (((originalSize) + (blockSize) - 1) / blockSize)) </b>/* 3 bytes per block */ + \<b> 1301 (blockSize) </b>/* One block of margin */ \<b> 1302 )) 1303</b><p> Similar to ZSTD_decompressionMargin(), but instead of computing the margin from 1304 the compressed frame, compute it from the original size and the blockSizeLog. 1305 See ZSTD_decompressionMargin() for details. 1306 1307 WARNING: This macro does not support multi-frame input, the input must be a single 1308 zstd frame. If you need that support use the function, or implement it yourself. 1309 1310 @param originalSize The original uncompressed size of the data. 1311 @param blockSize The block size == MIN(windowSize, ZSTD_BLOCKSIZE_MAX). 1312 Unless you explicitly set the windowLog smaller than 1313 ZSTD_BLOCKSIZELOG_MAX you can just use ZSTD_BLOCKSIZE_MAX. 1314 1315</p></pre><BR> 1316 1317<pre><b>typedef enum { 1318 ZSTD_sf_noBlockDelimiters = 0, </b>/* ZSTD_Sequence[] has no block delimiters, just sequences */<b> 1319 ZSTD_sf_explicitBlockDelimiters = 1 </b>/* ZSTD_Sequence[] contains explicit block delimiters */<b> 1320} ZSTD_SequenceFormat_e; 1321</b></pre><BR> 1322<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_sequenceBound(size_t srcSize); 1323</b><p> `srcSize` : size of the input buffer 1324 @return : upper-bound for the number of sequences that can be generated 1325 from a buffer of srcSize bytes 1326 1327 note : returns number of sequences - to get bytes, multiply by sizeof(ZSTD_Sequence). 1328 1329</p></pre><BR> 1330 1331<pre><b>ZSTD_DEPRECATED("For debugging only, will be replaced by ZSTD_extractSequences()") 1332ZSTDLIB_STATIC_API size_t 1333ZSTD_generateSequences(ZSTD_CCtx* zc, 1334 ZSTD_Sequence* outSeqs, size_t outSeqsCapacity, 1335 const void* src, size_t srcSize); 1336</b><p> WARNING: This function is meant for debugging and informational purposes ONLY! 1337 Its implementation is flawed, and it will be deleted in a future version. 1338 It is not guaranteed to succeed, as there are several cases where it will give 1339 up and fail. You should NOT use this function in production code. 1340 1341 This function is deprecated, and will be removed in a future version. 1342 1343 Generate sequences using ZSTD_compress2(), given a source buffer. 1344 1345 @param zc The compression context to be used for ZSTD_compress2(). Set any 1346 compression parameters you need on this context. 1347 @param outSeqs The output sequences buffer of size @p outSeqsSize 1348 @param outSeqsCapacity The size of the output sequences buffer. 1349 ZSTD_sequenceBound(srcSize) is an upper bound on the number 1350 of sequences that can be generated. 1351 @param src The source buffer to generate sequences from of size @p srcSize. 1352 @param srcSize The size of the source buffer. 1353 1354 Each block will end with a dummy sequence 1355 with offset == 0, matchLength == 0, and litLength == length of last literals. 1356 litLength may be == 0, and if so, then the sequence of (of: 0 ml: 0 ll: 0) 1357 simply acts as a block delimiter. 1358 1359 @returns The number of sequences generated, necessarily less than 1360 ZSTD_sequenceBound(srcSize), or an error code that can be checked 1361 with ZSTD_isError(). 1362 1363</p></pre><BR> 1364 1365<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_mergeBlockDelimiters(ZSTD_Sequence* sequences, size_t seqsSize); 1366</b><p> Given an array of ZSTD_Sequence, remove all sequences that represent block delimiters/last literals 1367 by merging them into the literals of the next sequence. 1368 1369 As such, the final generated result has no explicit representation of block boundaries, 1370 and the final last literals segment is not represented in the sequences. 1371 1372 The output of this function can be fed into ZSTD_compressSequences() with CCtx 1373 setting of ZSTD_c_blockDelimiters as ZSTD_sf_noBlockDelimiters 1374 @return : number of sequences left after merging 1375 1376</p></pre><BR> 1377 1378<pre><b>ZSTDLIB_STATIC_API size_t 1379ZSTD_compressSequences(ZSTD_CCtx* cctx, 1380 void* dst, size_t dstCapacity, 1381 const ZSTD_Sequence* inSeqs, size_t inSeqsSize, 1382 const void* src, size_t srcSize); 1383</b><p> Compress an array of ZSTD_Sequence, associated with @src buffer, into dst. 1384 @src contains the entire input (not just the literals). 1385 If @srcSize > sum(sequence.length), the remaining bytes are considered all literals 1386 If a dictionary is included, then the cctx should reference the dict (see: ZSTD_CCtx_refCDict(), ZSTD_CCtx_loadDictionary(), etc.). 1387 The entire source is compressed into a single frame. 1388 1389 The compression behavior changes based on cctx params. In particular: 1390 If ZSTD_c_blockDelimiters == ZSTD_sf_noBlockDelimiters, the array of ZSTD_Sequence is expected to contain 1391 no block delimiters (defined in ZSTD_Sequence). Block boundaries are roughly determined based on 1392 the block size derived from the cctx, and sequences may be split. This is the default setting. 1393 1394 If ZSTD_c_blockDelimiters == ZSTD_sf_explicitBlockDelimiters, the array of ZSTD_Sequence is expected to contain 1395 valid block delimiters (defined in ZSTD_Sequence). Behavior is undefined if no block delimiters are provided. 1396 1397 When ZSTD_c_blockDelimiters == ZSTD_sf_explicitBlockDelimiters, it's possible to decide generating repcodes 1398 using the advanced parameter ZSTD_c_repcodeResolution. Repcodes will improve compression ratio, though the benefit 1399 can vary greatly depending on Sequences. On the other hand, repcode resolution is an expensive operation. 1400 By default, it's disabled at low (<10) compression levels, and enabled above the threshold (>=10). 1401 ZSTD_c_repcodeResolution makes it possible to directly manage this processing in either direction. 1402 1403 If ZSTD_c_validateSequences == 0, this function blindly accepts the Sequences provided. Invalid Sequences cause undefined 1404 behavior. If ZSTD_c_validateSequences == 1, then the function will detect invalid Sequences (see doc/zstd_compression_format.md for 1405 specifics regarding offset/matchlength requirements) and then bail out and return an error. 1406 1407 In addition to the two adjustable experimental params, there are other important cctx params. 1408 - ZSTD_c_minMatch MUST be set as less than or equal to the smallest match generated by the match finder. It has a minimum value of ZSTD_MINMATCH_MIN. 1409 - ZSTD_c_compressionLevel accordingly adjusts the strength of the entropy coder, as it would in typical compression. 1410 - ZSTD_c_windowLog affects offset validation: this function will return an error at higher debug levels if a provided offset 1411 is larger than what the spec allows for a given window log and dictionary (if present). See: doc/zstd_compression_format.md 1412 1413 Note: Repcodes are, as of now, always re-calculated within this function, ZSTD_Sequence.rep is effectively unused. 1414 Dev Note: Once ability to ingest repcodes become available, the explicit block delims mode must respect those repcodes exactly, 1415 and cannot emit an RLE block that disagrees with the repcode history. 1416 @return : final compressed size, or a ZSTD error code. 1417 1418</p></pre><BR> 1419 1420<pre><b>ZSTDLIB_STATIC_API size_t 1421ZSTD_compressSequencesAndLiterals(ZSTD_CCtx* cctx, 1422 void* dst, size_t dstCapacity, 1423 const ZSTD_Sequence* inSeqs, size_t nbSequences, 1424 const void* literals, size_t litSize, size_t litCapacity, 1425 size_t decompressedSize); 1426</b><p> This is a variant of ZSTD_compressSequences() which, 1427 instead of receiving (src,srcSize) as input parameter, receives (literals,litSize), 1428 aka all the literals, already extracted and laid out into a single continuous buffer. 1429 This can be useful if the process generating the sequences also happens to generate the buffer of literals, 1430 thus skipping an extraction + caching stage. 1431 It's a speed optimization, useful when the right conditions are met, 1432 but it also features the following limitations: 1433 - Only supports explicit delimiter mode 1434 - Currently does not support Sequences validation (so input Sequences are trusted) 1435 - Not compatible with frame checksum, which must be disabled 1436 - If any block is incompressible, will fail and return an error 1437 - @litSize must be == sum of all @.litLength fields in @inSeqs. Any discrepancy will generate an error. 1438 - the buffer @literals must have a size @litCapacity which is larger than @litSize by at least 8 bytes. 1439 - @decompressedSize must be correct, and correspond to the sum of all Sequences. Any discrepancy will generate an error. 1440 @return : final compressed size, or a ZSTD error code. 1441 1442</p></pre><BR> 1443 1444<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_writeSkippableFrame(void* dst, size_t dstCapacity, 1445 const void* src, size_t srcSize, unsigned magicVariant); 1446</b><p> Generates a zstd skippable frame containing data given by src, and writes it to dst buffer. 1447 1448 Skippable frames begin with a 4-byte magic number. There are 16 possible choices of magic number, 1449 ranging from ZSTD_MAGIC_SKIPPABLE_START to ZSTD_MAGIC_SKIPPABLE_START+15. 1450 As such, the parameter magicVariant controls the exact skippable frame magic number variant used, so 1451 the magic number used will be ZSTD_MAGIC_SKIPPABLE_START + magicVariant. 1452 1453 Returns an error if destination buffer is not large enough, if the source size is not representable 1454 with a 4-byte unsigned int, or if the parameter magicVariant is greater than 15 (and therefore invalid). 1455 1456 @return : number of bytes written or a ZSTD error. 1457 1458</p></pre><BR> 1459 1460<pre><b>size_t ZSTD_readSkippableFrame(void* dst, size_t dstCapacity, unsigned* magicVariant, 1461 const void* src, size_t srcSize); 1462</b><p> Retrieves a zstd skippable frame containing data given by src, and writes it to dst buffer. 1463 1464 The parameter magicVariant will receive the magicVariant that was supplied when the frame was written, 1465 i.e. magicNumber - ZSTD_MAGIC_SKIPPABLE_START. This can be NULL if the caller is not interested 1466 in the magicVariant. 1467 1468 Returns an error if destination buffer is not large enough, or if the frame is not skippable. 1469 1470 @return : number of bytes written or a ZSTD error. 1471 1472</p></pre><BR> 1473 1474<pre><b>unsigned ZSTD_isSkippableFrame(const void* buffer, size_t size); 1475</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier for a skippable frame. 1476 1477</p></pre><BR> 1478 1479<a name="Chapter16"></a><h2>Memory management</h2><pre></pre> 1480 1481<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize(int maxCompressionLevel); 1482ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams); 1483ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params); 1484ZSTDLIB_STATIC_API size_t ZSTD_estimateDCtxSize(void); 1485</b><p> These functions make it possible to estimate memory usage 1486 of a future {D,C}Ctx, before its creation. 1487 This is useful in combination with ZSTD_initStatic(), 1488 which makes it possible to employ a static buffer for ZSTD_CCtx* state. 1489 1490 ZSTD_estimateCCtxSize() will provide a memory budget large enough 1491 to compress data of any size using one-shot compression ZSTD_compressCCtx() or ZSTD_compress2() 1492 associated with any compression level up to max specified one. 1493 The estimate will assume the input may be arbitrarily large, 1494 which is the worst case. 1495 1496 Note that the size estimation is specific for one-shot compression, 1497 it is not valid for streaming (see ZSTD_estimateCStreamSize*()) 1498 nor other potential ways of using a ZSTD_CCtx* state. 1499 1500 When srcSize can be bound by a known and rather "small" value, 1501 this knowledge can be used to provide a tighter budget estimation 1502 because the ZSTD_CCtx* state will need less memory for small inputs. 1503 This tighter estimation can be provided by employing more advanced functions 1504 ZSTD_estimateCCtxSize_usingCParams(), which can be used in tandem with ZSTD_getCParams(), 1505 and ZSTD_estimateCCtxSize_usingCCtxParams(), which can be used in tandem with ZSTD_CCtxParams_setParameter(). 1506 Both can be used to estimate memory using custom compression parameters and arbitrary srcSize limits. 1507 1508 Note : only single-threaded compression is supported. 1509 ZSTD_estimateCCtxSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1. 1510 1511</p></pre><BR> 1512 1513<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize(int maxCompressionLevel); 1514ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams); 1515ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params); 1516ZSTDLIB_STATIC_API size_t ZSTD_estimateDStreamSize(size_t maxWindowSize); 1517ZSTDLIB_STATIC_API size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize); 1518</b><p> ZSTD_estimateCStreamSize() will provide a memory budget large enough for streaming compression 1519 using any compression level up to the max specified one. 1520 It will also consider src size to be arbitrarily "large", which is a worst case scenario. 1521 If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation. 1522 ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel. 1523 ZSTD_estimateCStreamSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParams_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_c_nbWorkers is >= 1. 1524 Note : CStream size estimation is only correct for single-threaded compression. 1525 ZSTD_estimateCStreamSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1. 1526 Note 2 : ZSTD_estimateCStreamSize* functions are not compatible with the Block-Level Sequence Producer API at this time. 1527 Size estimates assume that no external sequence producer is registered. 1528 1529 ZSTD_DStream memory budget depends on frame's window Size. 1530 This information can be passed manually, using ZSTD_estimateDStreamSize, 1531 or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame(); 1532 Any frame requesting a window size larger than max specified one will be rejected. 1533 Note : if streaming is init with function ZSTD_init?Stream_usingDict(), 1534 an internal ?Dict will be created, which additional size is not estimated here. 1535 In this case, get total size by adding ZSTD_estimate?DictSize 1536 1537</p></pre><BR> 1538 1539<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel); 1540ZSTDLIB_STATIC_API size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod); 1541ZSTDLIB_STATIC_API size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod); 1542</b><p> ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict(). 1543 ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced(). 1544 Note : dictionaries created by reference (`ZSTD_dlm_byRef`) are logically smaller. 1545 1546</p></pre><BR> 1547 1548<pre><b>ZSTDLIB_STATIC_API ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize); 1549ZSTDLIB_STATIC_API ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticCCtx() */<b> 1550</b><p> Initialize an object using a pre-allocated fixed-size buffer. 1551 workspace: The memory area to emplace the object into. 1552 Provided pointer *must be 8-bytes aligned*. 1553 Buffer must outlive object. 1554 workspaceSize: Use ZSTD_estimate*Size() to determine 1555 how large workspace must be to support target scenario. 1556 @return : pointer to object (same address as workspace, just different type), 1557 or NULL if error (size too small, incorrect alignment, etc.) 1558 Note : zstd will never resize nor malloc() when using a static buffer. 1559 If the object requires more memory than available, 1560 zstd will just error out (typically ZSTD_error_memory_allocation). 1561 Note 2 : there is no corresponding "free" function. 1562 Since workspace is allocated externally, it must be freed externally too. 1563 Note 3 : cParams : use ZSTD_getCParams() to convert a compression level 1564 into its associated cParams. 1565 Limitation 1 : currently not compatible with internal dictionary creation, triggered by 1566 ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict(). 1567 Limitation 2 : static cctx currently not compatible with multi-threading. 1568 Limitation 3 : static dctx is incompatible with legacy support. 1569 1570</p></pre><BR> 1571 1572<pre><b>ZSTDLIB_STATIC_API ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticDCtx() */<b> 1573</b></pre><BR> 1574<pre><b>typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size); 1575typedef void (*ZSTD_freeFunction) (void* opaque, void* address); 1576typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem; 1577static 1578#ifdef __GNUC__ 1579__attribute__((__unused__)) 1580#endif 1581</b><p> These prototypes make it possible to pass your own allocation/free functions. 1582 ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below. 1583 All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones. 1584 1585</p></pre><BR> 1586 1587<pre><b>ZSTD_customMem const ZSTD_defaultCMem = { NULL, NULL, NULL }; </b>/**< this constant defers to stdlib's functions */<b> 1588</b></pre><BR> 1589<pre><b>typedef struct POOL_ctx_s ZSTD_threadPool; 1590ZSTDLIB_STATIC_API ZSTD_threadPool* ZSTD_createThreadPool(size_t numThreads); 1591ZSTDLIB_STATIC_API void ZSTD_freeThreadPool (ZSTD_threadPool* pool); </b>/* accept NULL pointer */<b> 1592ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refThreadPool(ZSTD_CCtx* cctx, ZSTD_threadPool* pool); 1593</b><p> These prototypes make it possible to share a thread pool among multiple compression contexts. 1594 This can limit resources for applications with multiple threads where each one uses 1595 a threaded compression mode (via ZSTD_c_nbWorkers parameter). 1596 ZSTD_createThreadPool creates a new thread pool with a given number of threads. 1597 Note that the lifetime of such pool must exist while being used. 1598 ZSTD_CCtx_refThreadPool assigns a thread pool to a context (use NULL argument value 1599 to use an internal thread pool). 1600 ZSTD_freeThreadPool frees a thread pool, accepts NULL pointer. 1601 1602</p></pre><BR> 1603 1604<a name="Chapter17"></a><h2>Advanced compression functions</h2><pre></pre> 1605 1606<pre><b>ZSTDLIB_STATIC_API ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel); 1607</b><p> Create a digested dictionary for compression 1608 Dictionary content is just referenced, not duplicated. 1609 As a consequence, `dictBuffer` **must** outlive CDict, 1610 and its content must remain unmodified throughout the lifetime of CDict. 1611 note: equivalent to ZSTD_createCDict_advanced(), with dictLoadMethod==ZSTD_dlm_byRef 1612</p></pre><BR> 1613 1614<pre><b>ZSTDLIB_STATIC_API ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize); 1615</b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize. 1616 `estimatedSrcSize` value is optional, select 0 if not known 1617</p></pre><BR> 1618 1619<pre><b>ZSTDLIB_STATIC_API ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize); 1620</b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`. 1621 All fields of `ZSTD_frameParameters` are set to default : contentSize=1, checksum=0, noDictID=0 1622</p></pre><BR> 1623 1624<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_checkCParams(ZSTD_compressionParameters params); 1625</b><p> Ensure param values remain within authorized range. 1626 @return 0 on success, or an error code (can be checked with ZSTD_isError()) 1627</p></pre><BR> 1628 1629<pre><b>ZSTDLIB_STATIC_API ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize); 1630</b><p> optimize params for a given `srcSize` and `dictSize`. 1631 `srcSize` can be unknown, in which case use ZSTD_CONTENTSIZE_UNKNOWN. 1632 `dictSize` must be `0` when there is no dictionary. 1633 cPar can be invalid : all parameters will be clamped within valid range in the @return struct. 1634 This function never fails (wide contract) 1635</p></pre><BR> 1636 1637<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setCParams(ZSTD_CCtx* cctx, ZSTD_compressionParameters cparams); 1638</b><p> Set all parameters provided within @p cparams into the working @p cctx. 1639 Note : if modifying parameters during compression (MT mode only), 1640 note that changes to the .windowLog parameter will be ignored. 1641 @return 0 on success, or an error code (can be checked with ZSTD_isError()). 1642 On failure, no parameters are updated. 1643 1644</p></pre><BR> 1645 1646<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setFParams(ZSTD_CCtx* cctx, ZSTD_frameParameters fparams); 1647</b><p> Set all parameters provided within @p fparams into the working @p cctx. 1648 @return 0 on success, or an error code (can be checked with ZSTD_isError()). 1649 1650</p></pre><BR> 1651 1652<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setParams(ZSTD_CCtx* cctx, ZSTD_parameters params); 1653</b><p> Set all parameters provided within @p params into the working @p cctx. 1654 @return 0 on success, or an error code (can be checked with ZSTD_isError()). 1655 1656</p></pre><BR> 1657 1658<pre><b>ZSTD_DEPRECATED("use ZSTD_compress2") 1659ZSTDLIB_STATIC_API 1660size_t ZSTD_compress_advanced(ZSTD_CCtx* cctx, 1661 void* dst, size_t dstCapacity, 1662 const void* src, size_t srcSize, 1663 const void* dict,size_t dictSize, 1664 ZSTD_parameters params); 1665</b><p> Note : this function is now DEPRECATED. 1666 It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_setParameter() and other parameter setters. 1667 This prototype will generate compilation warnings. 1668</p></pre><BR> 1669 1670<pre><b>ZSTD_DEPRECATED("use ZSTD_compress2 with ZSTD_CCtx_loadDictionary") 1671ZSTDLIB_STATIC_API 1672size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx, 1673 void* dst, size_t dstCapacity, 1674 const void* src, size_t srcSize, 1675 const ZSTD_CDict* cdict, 1676 ZSTD_frameParameters fParams); 1677</b><p> Note : this function is now DEPRECATED. 1678 It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_loadDictionary() and other parameter setters. 1679 This prototype will generate compilation warnings. 1680</p></pre><BR> 1681 1682<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize); 1683</b><p> Same as ZSTD_CCtx_loadDictionary(), but dictionary content is referenced, instead of being copied into CCtx. 1684 It saves some memory, but also requires that `dict` outlives its usage within `cctx` 1685</p></pre><BR> 1686 1687<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType); 1688</b><p> Same as ZSTD_CCtx_loadDictionary(), but gives finer control over 1689 how to load the dictionary (by copy ? by reference ?) 1690 and how to interpret it (automatic ? force raw mode ? full mode only ?) 1691</p></pre><BR> 1692 1693<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType); 1694</b><p> Same as ZSTD_CCtx_refPrefix(), but gives finer control over 1695 how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?) 1696</p></pre><BR> 1697 1698<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_getParameter(const ZSTD_CCtx* cctx, ZSTD_cParameter param, int* value); 1699</b><p> Get the requested compression parameter value, selected by enum ZSTD_cParameter, 1700 and store it into int* value. 1701 @return : 0, or an error code (which can be tested with ZSTD_isError()). 1702 1703</p></pre><BR> 1704 1705<pre><b>ZSTDLIB_STATIC_API ZSTD_CCtx_params* ZSTD_createCCtxParams(void); 1706ZSTDLIB_STATIC_API size_t ZSTD_freeCCtxParams(ZSTD_CCtx_params* params); </b>/* accept NULL pointer */<b> 1707</b><p> Quick howto : 1708 - ZSTD_createCCtxParams() : Create a ZSTD_CCtx_params structure 1709 - ZSTD_CCtxParams_setParameter() : Push parameters one by one into 1710 an existing ZSTD_CCtx_params structure. 1711 This is similar to 1712 ZSTD_CCtx_setParameter(). 1713 - ZSTD_CCtx_setParametersUsingCCtxParams() : Apply parameters to 1714 an existing CCtx. 1715 These parameters will be applied to 1716 all subsequent frames. 1717 - ZSTD_compressStream2() : Do compression using the CCtx. 1718 - ZSTD_freeCCtxParams() : Free the memory, accept NULL pointer. 1719 1720 This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams() 1721 for static allocation of CCtx for single-threaded compression. 1722 1723</p></pre><BR> 1724 1725<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_reset(ZSTD_CCtx_params* params); 1726</b><p> Reset params to default values. 1727 1728</p></pre><BR> 1729 1730<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_init(ZSTD_CCtx_params* cctxParams, int compressionLevel); 1731</b><p> Initializes the compression parameters of cctxParams according to 1732 compression level. All other parameters are reset to their default values. 1733 1734</p></pre><BR> 1735 1736<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_init_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params); 1737</b><p> Initializes the compression and frame parameters of cctxParams according to 1738 params. All other parameters are reset to their default values. 1739 1740</p></pre><BR> 1741 1742<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int value); 1743</b><p> Similar to ZSTD_CCtx_setParameter. 1744 Set one compression parameter, selected by enum ZSTD_cParameter. 1745 Parameters must be applied to a ZSTD_CCtx using 1746 ZSTD_CCtx_setParametersUsingCCtxParams(). 1747 @result : a code representing success or failure (which can be tested with 1748 ZSTD_isError()). 1749 1750</p></pre><BR> 1751 1752<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_getParameter(const ZSTD_CCtx_params* params, ZSTD_cParameter param, int* value); 1753</b><p> Similar to ZSTD_CCtx_getParameter. 1754 Get the requested value of one compression parameter, selected by enum ZSTD_cParameter. 1755 @result : 0, or an error code (which can be tested with ZSTD_isError()). 1756 1757</p></pre><BR> 1758 1759<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setParametersUsingCCtxParams( 1760 ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params); 1761</b><p> Apply a set of ZSTD_CCtx_params to the compression context. 1762 This can be done even after compression is started, 1763 if nbWorkers==0, this will have no impact until a new compression is started. 1764 if nbWorkers>=1, new parameters will be picked up at next job, 1765 with a few restrictions (windowLog, pledgedSrcSize, nbWorkers, jobSize, and overlapLog are not updated). 1766 1767</p></pre><BR> 1768 1769<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_compressStream2_simpleArgs ( 1770 ZSTD_CCtx* cctx, 1771 void* dst, size_t dstCapacity, size_t* dstPos, 1772 const void* src, size_t srcSize, size_t* srcPos, 1773 ZSTD_EndDirective endOp); 1774</b><p> Same as ZSTD_compressStream2(), 1775 but using only integral types as arguments. 1776 This variant might be helpful for binders from dynamic languages 1777 which have troubles handling structures containing memory pointers. 1778 1779</p></pre><BR> 1780 1781<a name="Chapter18"></a><h2>Advanced decompression functions</h2><pre></pre> 1782 1783<pre><b>ZSTDLIB_STATIC_API unsigned ZSTD_isFrame(const void* buffer, size_t size); 1784</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier. 1785 Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0. 1786 Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled. 1787 Note 3 : Skippable Frame Identifiers are considered valid. 1788</p></pre><BR> 1789 1790<pre><b>ZSTDLIB_STATIC_API ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize); 1791</b><p> Create a digested dictionary, ready to start decompression operation without startup delay. 1792 Dictionary content is referenced, and therefore stays in dictBuffer. 1793 It is important that dictBuffer outlives DDict, 1794 it must remain read accessible throughout the lifetime of DDict 1795</p></pre><BR> 1796 1797<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize); 1798</b><p> Same as ZSTD_DCtx_loadDictionary(), 1799 but references `dict` content instead of copying it into `dctx`. 1800 This saves memory if `dict` remains around., 1801 However, it's imperative that `dict` remains accessible (and unmodified) while being used, so it must outlive decompression. 1802</p></pre><BR> 1803 1804<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType); 1805</b><p> Same as ZSTD_DCtx_loadDictionary(), 1806 but gives direct control over 1807 how to load the dictionary (by copy ? by reference ?) 1808 and how to interpret it (automatic ? force raw mode ? full mode only ?). 1809</p></pre><BR> 1810 1811<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType); 1812</b><p> Same as ZSTD_DCtx_refPrefix(), but gives finer control over 1813 how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?) 1814</p></pre><BR> 1815 1816<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize); 1817</b><p> Refuses allocating internal buffers for frames requiring a window size larger than provided limit. 1818 This protects a decoder context from reserving too much memory for itself (potential attack scenario). 1819 This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode. 1820 By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT) 1821 @return : 0, or an error code (which can be tested using ZSTD_isError()). 1822 1823</p></pre><BR> 1824 1825<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_getParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int* value); 1826</b><p> Get the requested decompression parameter value, selected by enum ZSTD_dParameter, 1827 and store it into int* value. 1828 @return : 0, or an error code (which can be tested with ZSTD_isError()). 1829 1830</p></pre><BR> 1831 1832<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_setParameter() instead") 1833ZSTDLIB_STATIC_API 1834size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format); 1835</b><p> This function is REDUNDANT. Prefer ZSTD_DCtx_setParameter(). 1836 Instruct the decoder context about what kind of data to decode next. 1837 This instruction is mandatory to decode data without a fully-formed header, 1838 such ZSTD_f_zstd1_magicless for example. 1839 @return : 0, or an error code (which can be tested using ZSTD_isError()). 1840</p></pre><BR> 1841 1842<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decompressStream_simpleArgs ( 1843 ZSTD_DCtx* dctx, 1844 void* dst, size_t dstCapacity, size_t* dstPos, 1845 const void* src, size_t srcSize, size_t* srcPos); 1846</b><p> Same as ZSTD_decompressStream(), 1847 but using only integral types as arguments. 1848 This can be helpful for binders from dynamic languages 1849 which have troubles handling structures containing memory pointers. 1850 1851</p></pre><BR> 1852 1853<a name="Chapter19"></a><h2>Advanced streaming functions</h2><pre> Warning : most of these functions are now redundant with the Advanced API. 1854 Once Advanced API reaches "stable" status, 1855 redundant functions will be deprecated, and then at some point removed. 1856<BR></pre> 1857 1858<h3>Advanced Streaming compression functions</h3><pre></pre><b><pre></pre></b><BR> 1859<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions") 1860ZSTDLIB_STATIC_API 1861size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs, 1862 int compressionLevel, 1863 unsigned long long pledgedSrcSize); 1864</b><p> This function is DEPRECATED, and equivalent to: 1865 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); 1866 ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any) 1867 ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel); 1868 ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); 1869 1870 pledgedSrcSize must be correct. If it is not known at init time, use 1871 ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs, 1872 "0" also disables frame content size field. It may be enabled in the future. 1873 This prototype will generate compilation warnings. 1874 1875</p></pre><BR> 1876 1877<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions") 1878ZSTDLIB_STATIC_API 1879size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs, 1880 const void* dict, size_t dictSize, 1881 int compressionLevel); 1882</b><p> This function is DEPRECATED, and is equivalent to: 1883 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); 1884 ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel); 1885 ZSTD_CCtx_loadDictionary(zcs, dict, dictSize); 1886 1887 Creates of an internal CDict (incompatible with static CCtx), except if 1888 dict == NULL or dictSize < 8, in which case no dict is used. 1889 Note: dict is loaded with ZSTD_dct_auto (treated as a full zstd dictionary if 1890 it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy. 1891 This prototype will generate compilation warnings. 1892 1893</p></pre><BR> 1894 1895<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions") 1896ZSTDLIB_STATIC_API 1897size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs, 1898 const void* dict, size_t dictSize, 1899 ZSTD_parameters params, 1900 unsigned long long pledgedSrcSize); 1901</b><p> This function is DEPRECATED, and is equivalent to: 1902 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); 1903 ZSTD_CCtx_setParams(zcs, params); 1904 ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); 1905 ZSTD_CCtx_loadDictionary(zcs, dict, dictSize); 1906 1907 dict is loaded with ZSTD_dct_auto and ZSTD_dlm_byCopy. 1908 pledgedSrcSize must be correct. 1909 If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN. 1910 This prototype will generate compilation warnings. 1911 1912</p></pre><BR> 1913 1914<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions") 1915ZSTDLIB_STATIC_API 1916size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict); 1917</b><p> This function is DEPRECATED, and equivalent to: 1918 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); 1919 ZSTD_CCtx_refCDict(zcs, cdict); 1920 1921 note : cdict will just be referenced, and must outlive compression session 1922 This prototype will generate compilation warnings. 1923 1924</p></pre><BR> 1925 1926<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions") 1927ZSTDLIB_STATIC_API 1928size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs, 1929 const ZSTD_CDict* cdict, 1930 ZSTD_frameParameters fParams, 1931 unsigned long long pledgedSrcSize); 1932</b><p> This function is DEPRECATED, and is equivalent to: 1933 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); 1934 ZSTD_CCtx_setFParams(zcs, fParams); 1935 ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); 1936 ZSTD_CCtx_refCDict(zcs, cdict); 1937 1938 same as ZSTD_initCStream_usingCDict(), with control over frame parameters. 1939 pledgedSrcSize must be correct. If srcSize is not known at init time, use 1940 value ZSTD_CONTENTSIZE_UNKNOWN. 1941 This prototype will generate compilation warnings. 1942 1943</p></pre><BR> 1944 1945<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions") 1946ZSTDLIB_STATIC_API 1947size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize); 1948</b><p> This function is DEPRECATED, and is equivalent to: 1949 ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only); 1950 ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize); 1951 Note: ZSTD_resetCStream() interprets pledgedSrcSize == 0 as ZSTD_CONTENTSIZE_UNKNOWN, but 1952 ZSTD_CCtx_setPledgedSrcSize() does not do the same, so ZSTD_CONTENTSIZE_UNKNOWN must be 1953 explicitly specified. 1954 1955 start a new frame, using same parameters from previous frame. 1956 This is typically useful to skip dictionary loading stage, since it will reuse it in-place. 1957 Note that zcs must be init at least once before using ZSTD_resetCStream(). 1958 If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN. 1959 If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end. 1960 For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs, 1961 but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead. 1962 @return : 0, or an error code (which can be tested using ZSTD_isError()) 1963 This prototype will generate compilation warnings. 1964 1965</p></pre><BR> 1966 1967<pre><b>typedef struct { 1968 unsigned long long ingested; </b>/* nb input bytes read and buffered */<b> 1969 unsigned long long consumed; </b>/* nb input bytes actually compressed */<b> 1970 unsigned long long produced; </b>/* nb of compressed bytes generated and buffered */<b> 1971 unsigned long long flushed; </b>/* nb of compressed bytes flushed : not provided; can be tracked from caller side */<b> 1972 unsigned currentJobID; </b>/* MT only : latest started job nb */<b> 1973 unsigned nbActiveWorkers; </b>/* MT only : nb of workers actively compressing at probe time */<b> 1974} ZSTD_frameProgression; 1975</b></pre><BR> 1976<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_toFlushNow(ZSTD_CCtx* cctx); 1977</b><p> Tell how many bytes are ready to be flushed immediately. 1978 Useful for multithreading scenarios (nbWorkers >= 1). 1979 Probe the oldest active job, defined as oldest job not yet entirely flushed, 1980 and check its output buffer. 1981 @return : amount of data stored in oldest job and ready to be flushed immediately. 1982 if @return == 0, it means either : 1983 + there is no active job (could be checked with ZSTD_frameProgression()), or 1984 + oldest job is still actively compressing data, 1985 but everything it has produced has also been flushed so far, 1986 therefore flush speed is limited by production speed of oldest job 1987 irrespective of the speed of concurrent (and newer) jobs. 1988 1989</p></pre><BR> 1990 1991<h3>Advanced Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR> 1992<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset + ZSTD_DCtx_loadDictionary, see zstd.h for detailed instructions") 1993ZSTDLIB_STATIC_API size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize); 1994</b><p> 1995 ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); 1996 ZSTD_DCtx_loadDictionary(zds, dict, dictSize); 1997 1998 note: no dictionary will be used if dict == NULL or dictSize < 8 1999 2000</p></pre><BR> 2001 2002<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset + ZSTD_DCtx_refDDict, see zstd.h for detailed instructions") 2003ZSTDLIB_STATIC_API size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict); 2004</b><p> 2005 ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); 2006 ZSTD_DCtx_refDDict(zds, ddict); 2007 2008 note : ddict is referenced, it must outlive decompression session 2009 2010</p></pre><BR> 2011 2012<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset, see zstd.h for detailed instructions") 2013ZSTDLIB_STATIC_API size_t ZSTD_resetDStream(ZSTD_DStream* zds); 2014</b><p> 2015 ZSTD_DCtx_reset(zds, ZSTD_reset_session_only); 2016 2017 reuse decompression parameters from previous init; saves dictionary loading 2018 2019</p></pre><BR> 2020 2021<pre><b>ZSTDLIB_STATIC_API void 2022ZSTD_registerSequenceProducer( 2023 ZSTD_CCtx* cctx, 2024 void* sequenceProducerState, 2025 ZSTD_sequenceProducer_F sequenceProducer 2026); 2027</b><p> Instruct zstd to use a block-level external sequence producer function. 2028 2029 The sequenceProducerState must be initialized by the caller, and the caller is 2030 responsible for managing its lifetime. This parameter is sticky across 2031 compressions. It will remain set until the user explicitly resets compression 2032 parameters. 2033 2034 Sequence producer registration is considered to be an "advanced parameter", 2035 part of the "advanced API". This means it will only have an effect on compression 2036 APIs which respect advanced parameters, such as compress2() and compressStream2(). 2037 Older compression APIs such as compressCCtx(), which predate the introduction of 2038 "advanced parameters", will ignore any external sequence producer setting. 2039 2040 The sequence producer can be "cleared" by registering a NULL function pointer. This 2041 removes all limitations described above in the "LIMITATIONS" section of the API docs. 2042 2043 The user is strongly encouraged to read the full API documentation (above) before 2044 calling this function. 2045</p></pre><BR> 2046 2047<pre><b>ZSTDLIB_STATIC_API void 2048ZSTD_CCtxParams_registerSequenceProducer( 2049 ZSTD_CCtx_params* params, 2050 void* sequenceProducerState, 2051 ZSTD_sequenceProducer_F sequenceProducer 2052); 2053</b><p> Same as ZSTD_registerSequenceProducer(), but operates on ZSTD_CCtx_params. 2054 This is used for accurate size estimation with ZSTD_estimateCCtxSize_usingCCtxParams(), 2055 which is needed when creating a ZSTD_CCtx with ZSTD_initStaticCCtx(). 2056 2057 If you are using the external sequence producer API in a scenario where ZSTD_initStaticCCtx() 2058 is required, then this function is for you. Otherwise, you probably don't need it. 2059 2060 See tests/zstreamtest.c for example usage. 2061</p></pre><BR> 2062 2063<a name="Chapter20"></a><h2>Buffer-less and synchronous inner streaming functions (DEPRECATED)</h2><pre> 2064 This API is deprecated, and will be removed in a future version. 2065 It allows streaming (de)compression with user allocated buffers. 2066 However, it is hard to use, and not as well tested as the rest of 2067 our API. 2068 2069 Please use the normal streaming API instead: ZSTD_compressStream2, 2070 and ZSTD_decompressStream. 2071 If there is functionality that you need, but it doesn't provide, 2072 please open an issue on our GitHub. 2073 2074<BR></pre> 2075 2076<a name="Chapter21"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre> 2077 A ZSTD_CCtx object is required to track streaming operations. 2078 Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource. 2079 ZSTD_CCtx object can be reused multiple times within successive compression operations. 2080 2081 Start by initializing a context. 2082 Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression. 2083 2084 Then, consume your input using ZSTD_compressContinue(). 2085 There are some important considerations to keep in mind when using this advanced function : 2086 - ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only. 2087 - Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks. 2088 - Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario. 2089 Worst case evaluation is provided by ZSTD_compressBound(). 2090 ZSTD_compressContinue() doesn't guarantee recover after a failed compression. 2091 - ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog). 2092 It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks) 2093 - ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps. 2094 In which case, it will "discard" the relevant memory section from its history. 2095 2096 Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum. 2097 It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame. 2098 Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders. 2099 2100 `ZSTD_CCtx` object can be reused (ZSTD_compressBegin()) to compress again. 2101<BR></pre> 2102 2103<h3>Buffer-less streaming compression functions</h3><pre></pre><b><pre>ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.") 2104ZSTDLIB_STATIC_API size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel); 2105ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.") 2106ZSTDLIB_STATIC_API size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel); 2107ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.") 2108ZSTDLIB_STATIC_API size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b> 2109</pre></b><BR> 2110<pre><b>size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx, unsigned long long pledgedSrcSize); </b>/**< note: if pledgedSrcSize is not known, use ZSTD_CONTENTSIZE_UNKNOWN */<b> 2111</b></pre><BR> 2112<pre><b>size_t ZSTD_compressBegin_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_parameters params, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize : If srcSize is not known at init time, use ZSTD_CONTENTSIZE_UNKNOWN */<b> 2113</b></pre><BR> 2114<a name="Chapter22"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre> 2115 A ZSTD_DCtx object is required to track streaming operations. 2116 Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it. 2117 A ZSTD_DCtx object can be reused multiple times. 2118 2119 First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader(). 2120 Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough. 2121 Data fragment must be large enough to ensure successful decoding. 2122 `ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough. 2123 result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled. 2124 >0 : `srcSize` is too small, please provide at least result bytes on next attempt. 2125 errorCode, which can be tested using ZSTD_isError(). 2126 2127 It fills a ZSTD_FrameHeader structure with important information to correctly decode the frame, 2128 such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`). 2129 Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information. 2130 As a consequence, check that values remain within valid application range. 2131 For example, do not allocate memory blindly, check that `windowSize` is within expectation. 2132 Each application can set its own limits, depending on local restrictions. 2133 For extended interoperability, it is recommended to support `windowSize` of at least 8 MB. 2134 2135 ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes. 2136 ZSTD_decompressContinue() is very sensitive to contiguity, 2137 if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place, 2138 or that previous contiguous segment is large enough to properly handle maximum back-reference distance. 2139 There are multiple ways to guarantee this condition. 2140 2141 The most memory efficient way is to use a round buffer of sufficient size. 2142 Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(), 2143 which can return an error code if required value is too large for current system (in 32-bits mode). 2144 In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one, 2145 up to the moment there is not enough room left in the buffer to guarantee decoding another full block, 2146 which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`. 2147 At which point, decoding can resume from the beginning of the buffer. 2148 Note that already decoded data stored in the buffer should be flushed before being overwritten. 2149 2150 There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory. 2151 2152 Finally, if you control the compression process, you can also ignore all buffer size rules, 2153 as long as the encoder and decoder progress in "lock-step", 2154 aka use exactly the same buffer sizes, break contiguity at the same place, etc. 2155 2156 Once buffers are setup, start decompression, with ZSTD_decompressBegin(). 2157 If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict(). 2158 2159 Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively. 2160 ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue(). 2161 ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail. 2162 2163 result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity). 2164 It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item. 2165 It can also be an error code, which can be tested with ZSTD_isError(). 2166 2167 A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero. 2168 Context can then be reset to start a new decompression. 2169 2170 Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType(). 2171 This information is not required to properly decode a frame. 2172 2173 == Special case : skippable frames 2174 2175 Skippable frames allow integration of user-defined data into a flow of concatenated frames. 2176 Skippable frames will be ignored (skipped) by decompressor. 2177 The format of skippable frames is as follows : 2178 a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F 2179 b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits 2180 c) Frame Content - any content (User Data) of length equal to Frame Size 2181 For skippable frames ZSTD_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame. 2182 For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content. 2183<BR></pre> 2184 2185<h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR> 2186<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long long frameContentSize); </b>/**< when frame content size is not known, pass in frameContentSize == ZSTD_CONTENTSIZE_UNKNOWN */<b> 2187</b></pre><BR> 2188<pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e; 2189</b></pre><BR> 2190<a name="Chapter23"></a><h2>Block level API (DEPRECATED)</h2><pre></pre> 2191 2192<pre><b></b><p> You can get the frame header down to 2 bytes by setting: 2193 - ZSTD_c_format = ZSTD_f_zstd1_magicless 2194 - ZSTD_c_contentSizeFlag = 0 2195 - ZSTD_c_checksumFlag = 0 2196 - ZSTD_c_dictIDFlag = 0 2197 2198 This API is not as well tested as our normal API, so we recommend not using it. 2199 We will be removing it in a future version. If the normal API doesn't provide 2200 the functionality you need, please open a GitHub issue. 2201 2202 Block functions produce and decode raw zstd blocks, without frame metadata. 2203 Frame metadata cost is typically ~12 bytes, which can be non-negligible for very small blocks (< 100 bytes). 2204 But users will have to take in charge needed metadata to regenerate data, such as compressed and content sizes. 2205 2206 A few rules to respect : 2207 - Compressing and decompressing require a context structure 2208 + Use ZSTD_createCCtx() and ZSTD_createDCtx() 2209 - It is necessary to init context before starting 2210 + compression : any ZSTD_compressBegin*() variant, including with dictionary 2211 + decompression : any ZSTD_decompressBegin*() variant, including with dictionary 2212 - Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB 2213 + If input is larger than a block size, it's necessary to split input data into multiple blocks 2214 + For inputs larger than a single block, consider using regular ZSTD_compress() instead. 2215 Frame metadata is not that costly, and quickly becomes negligible as source size grows larger than a block. 2216 - When a block is considered not compressible enough, ZSTD_compressBlock() result will be 0 (zero) ! 2217 ===> In which case, nothing is produced into `dst` ! 2218 + User __must__ test for such outcome and deal directly with uncompressed data 2219 + A block cannot be declared incompressible if ZSTD_compressBlock() return value was != 0. 2220 Doing so would mess up with statistics history, leading to potential data corruption. 2221 + ZSTD_decompressBlock() _doesn't accept uncompressed data as input_ !! 2222 + In case of multiple successive blocks, should some of them be uncompressed, 2223 decoder must be informed of their existence in order to follow proper history. 2224 Use ZSTD_insertBlock() for such a case. 2225</p></pre><BR> 2226 2227<h3>Raw zstd block functions</h3><pre></pre><b><pre>ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.") 2228ZSTDLIB_STATIC_API size_t ZSTD_getBlockSize (const ZSTD_CCtx* cctx); 2229ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.") 2230ZSTDLIB_STATIC_API size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); 2231ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.") 2232ZSTDLIB_STATIC_API size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize); 2233ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.") 2234ZSTDLIB_STATIC_API size_t ZSTD_insertBlock (ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize); </b>/**< insert uncompressed block into `dctx` history. Useful for multi-blocks decompression. */<b> 2235</pre></b><BR> 2236</html> 2237</body> 2238